diff --git a/acl.go b/acl.go
new file mode 100644
index 0000000..a3b85b1
--- /dev/null
+++ b/acl.go
@@ -0,0 +1,193 @@
+package graphvent
+
+import (
+  "github.com/google/uuid"
+  "slices"
+  "time"
+)
+
+type ACLSignal struct {
+  SignalHeader
+  Principal NodeID `gv:"principal"`
+  Action Tree `gv:"tree"`
+}
+
+func NewACLSignal(principal NodeID, action Tree) *ACLSignal {
+  return &ACLSignal{
+    SignalHeader: NewSignalHeader(Direct),
+    Principal: principal,
+    Action: action,
+  }
+}
+
+var DefaultACLPolicy = NewAllNodesPolicy(Tree{
+  SerializedType(ACLSignalType): nil,
+})
+
+func (signal ACLSignal) Permission() Tree {
+  return Tree{
+    SerializedType(ACLSignalType): nil,
+  }
+}
+
+type ACLExt struct {
+  Policies []Policy `gv:"policies"`
+  PendingACLs map[uuid.UUID]PendingACL `gv:"pending_acls"`
+  Pending map[uuid.UUID]PendingSignal `gv:"pending"`
+}
+
+func NewACLExt(policies []Policy) *ACLExt {
+  return &ACLExt{
+    Policies: policies,
+    PendingACLs: map[uuid.UUID]PendingACL{},
+    Pending: map[uuid.UUID]PendingSignal{},
+  }
+}
+
+func (ext *ACLExt) Process(ctx *Context, node *Node, source NodeID, signal Signal) (Messages, Changes) {
+  response, is_response := signal.(ResponseSignal)
+  if is_response == true {
+    var messages Messages = nil
+    var changes Changes = nil
+    info, waiting := ext.Pending[response.ResponseID()]
+    if waiting == true {
+      changes = changes.Add("response_processed")
+      delete(ext.Pending, response.ResponseID())
+      if response.ID() != info.Timeout {
+        err := node.DequeueSignal(info.Timeout)
+        if err != nil {
+          ctx.Log.Logf("acl", "timeout dequeue error: %s", err)
+        }
+      }
+
+      acl_info, found := ext.PendingACLs[info.ID]
+      if found == true {
+        acl_info.Counter -= 1
+        acl_info.Responses = append(acl_info.Responses, response)
+
+        policy_index := slices.IndexFunc(ext.Policies, func(policy Policy) bool {
+          return policy.ID() == info.Policy
+        })
+
+        if policy_index == -1 {
+          ctx.Log.Logf("acl", "pending signal for nonexistent policy")
+          delete(ext.PendingACLs, info.ID)
+          err := node.DequeueSignal(acl_info.TimeoutID)
+          if err != nil {
+            ctx.Log.Logf("acl", "acl proxy timeout dequeue error: %s", err)
+          }
+        } else {
+          if ext.Policies[policy_index].ContinueAllows(ctx, acl_info, response) == Allow {
+            delete(ext.PendingACLs, info.ID)
+            ctx.Log.Logf("acl", "Request delayed allow")
+            messages = messages.Add(ctx, node.ID, node.Key, NewSuccessSignal(info.ID), acl_info.Source)
+            changes = changes.Add("acl_passed")
+            err := node.DequeueSignal(acl_info.TimeoutID)
+            if err != nil {
+              ctx.Log.Logf("acl", "acl proxy timeout dequeue error: %s", err)
+            }
+          } else if acl_info.Counter == 0 {
+            delete(ext.PendingACLs, info.ID)
+            ctx.Log.Logf("acl", "Request delayed deny")
+            messages = messages.Add(ctx, node.ID, node.Key, NewErrorSignal(info.ID, "acl_denied"), acl_info.Source)
+            changes = changes.Add("acl_blocked")
+            err := node.DequeueSignal(acl_info.TimeoutID)
+            if err != nil {
+              ctx.Log.Logf("acl", "acl proxy timeout dequeue error: %s", err)
+            }
+          } else {
+            node.PendingACLs[info.ID] = acl_info
+            changes = changes.Add("acl_processed")
+          }
+        }
+      }
+    }
+    return messages, changes
+  }
+
+  var messages Messages = nil
+  var changes Changes = nil
+
+  switch sig := signal.(type) {
+  case *ACLSignal:
+    var acl_messages map[uuid.UUID]Messages = nil
+    denied := true
+    for _, policy := range(ext.Policies) {
+      policy_messages, result := policy.Allows(ctx, sig.Principal, sig.Action, node)
+      if result == Allow {
+        denied = false
+        break
+      } else if result == Pending {
+        if len(policy_messages) == 0 {
+          ctx.Log.Logf("acl", "Pending result for %s with no messages returned", policy.ID())
+          continue
+        } else if acl_messages == nil {
+          acl_messages = map[uuid.UUID]Messages{}
+          denied = false
+        }
+
+        acl_messages[policy.ID()] = policy_messages
+        ctx.Log.Logf("acl", "Pending result for %s:%s - %+v", node.ID, policy.ID(), acl_messages)
+      }
+    }
+
+    if denied == true {
+      ctx.Log.Logf("acl", "Request denied")
+      messages = messages.Add(ctx, node.ID, node.Key, NewErrorSignal(sig.Id, "acl_denied"), source)
+    } else if acl_messages != nil {
+      ctx.Log.Logf("acl", "Request pending")
+      changes = changes.Add("acl_pending")
+      total_messages := 0
+      // TODO: reasonable timeout/configurable
+      timeout_time := time.Now().Add(time.Second)
+      for policy_id, policy_messages := range(acl_messages) {
+        total_messages += len(policy_messages)
+        for _, message := range(policy_messages) {
+          // Create timeout signal and add the ID to Pending
+          timeout_signal := NewTimeoutSignal(message.Signal.ID())
+          ext.Pending[message.Signal.ID()] = PendingSignal{
+            Policy: policy_id,
+            Timeout: timeout_signal.Id,
+            ID: sig.Id,
+          }
+          node.QueueSignal(timeout_time, timeout_signal)
+          messages = append(messages, message)
+        }
+      }
+
+      acl_timeout := NewACLTimeoutSignal(sig.Id)
+      node.QueueSignal(timeout_time, acl_timeout)
+      ext.PendingACLs[sig.Id] = PendingACL{
+        Counter: total_messages,
+        Responses: []ResponseSignal{},
+        TimeoutID: acl_timeout.Id,
+        Action: sig.Action,
+        Principal: sig.Principal,
+
+        Source: source,
+        Signal: signal,
+      }
+    } else {
+      ctx.Log.Logf("acl", "Request allowed")
+      messages = messages.Add(ctx, node.ID, node.Key, NewSuccessSignal(sig.Id), source)
+    }
+    // Test an action against the policy list, sending any intermediate signals necessary and seeting Pending and PendingACLs accordingly. Add a TimeoutSignal for every message awaiting a response, and an ACLTimeoutSignal for the overall request
+  case *ACLTimeoutSignal:
+    acl_info, exists := ext.PendingACLs[sig.ReqID]
+    if exists == true {
+      delete(ext.PendingACLs, sig.ReqID)
+      ctx.Log.Logf("acl", "Request timeout deny")
+      messages = messages.Add(ctx, node.ID, node.Key, NewErrorSignal(sig.ReqID, "acl_timeout"), acl_info.Source)
+      changes = changes.Add("acl_timeout")
+      err := node.DequeueSignal(acl_info.TimeoutID)
+      if err != nil {
+        ctx.Log.Logf("acl", "acl proxy timeout dequeue error: %s", err)
+      }
+    } else {
+      ctx.Log.Logf("acl", "ACL_TIMEOUT_SIGNAL for passed acl")
+    }
+    // Delete from PendingACLs
+  }
+
+  return messages, changes
+}
diff --git a/acl_test.go b/acl_test.go
new file mode 100644
index 0000000..b28ea5d
--- /dev/null
+++ b/acl_test.go
@@ -0,0 +1,91 @@
+package graphvent
+
+import (
+  "testing"
+  "time"
+  "reflect"
+)
+
+func checkSignal[S Signal](t *testing.T, signal Signal, check func(S)){
+  response_casted, cast_ok := signal.(S)
+  if cast_ok == false {
+    error_signal, is_error := signal.(*ErrorSignal)
+    if is_error {
+      t.Fatal(error_signal.Error)
+    }
+    t.Fatalf("Response of wrong type %s", reflect.TypeOf(signal))
+  }
+
+  check(response_casted)
+}
+
+func testSendACL[S Signal](t *testing.T, ctx *Context, listener *Node, action Tree, policies []Policy, check func(S)){
+  acl_node, err := NewNode(ctx, nil, BaseNodeType, 100, []Policy{DefaultACLPolicy}, NewACLExt(policies))
+  fatalErr(t, err)
+
+  acl_signal := NewACLSignal(listener.ID, action)
+  response := testSend(t, ctx, acl_signal, listener, acl_node)
+
+  checkSignal(t, response, check)
+}
+
+func testErrorSignal(t *testing.T, error_string string) func(*ErrorSignal){
+  return func(response *ErrorSignal) {
+    if response.Error != error_string {
+      t.Fatalf("Wrong error: %s", response.Error)
+    }
+  }
+}
+
+func testSuccess(*SuccessSignal){}
+
+func testSend(t *testing.T, ctx *Context, signal Signal, source, destination *Node) ResponseSignal {
+  source_listener, err := GetExt[*ListenerExt](source, ListenerExtType)
+  fatalErr(t, err)
+
+  messages := Messages{}
+  messages = messages.Add(ctx, source.ID, source.Key, signal, destination.ID)
+  fatalErr(t, ctx.Send(messages))
+
+  response, err := WaitForResponse(source_listener.Chan, time.Millisecond*10, signal.ID())
+  fatalErr(t, err)
+
+  return response
+}
+
+func TestACLBasic(t *testing.T) {
+  ctx := logTestContext(t, []string{"test", "acl"})
+
+  listener, err := NewNode(ctx, nil, BaseNodeType, 100, nil, NewListenerExt(100))
+  fatalErr(t, err)
+
+  testSendACL(t, ctx, listener, nil, nil, testErrorSignal(t, "acl_denied"))
+
+  testSendACL(t, ctx, listener, nil, []Policy{NewAllNodesPolicy(nil)}, testSuccess)
+
+  group, err := NewNode(ctx, nil, GroupNodeType, 100, []Policy{
+    DefaultGroupPolicy,
+    NewPerNodePolicy(map[NodeID]Tree{
+      listener.ID: {
+        SerializedType(AddMemberSignalType): nil,
+      },
+    }),
+  }, NewGroupExt(nil))
+  fatalErr(t, err)
+
+  testSendACL(t, ctx, listener, nil, []Policy{
+    NewMemberOfPolicy(map[NodeID]Tree{
+      group.ID: nil,
+    }),
+  }, testErrorSignal(t, "acl_denied"))
+
+  add_member_signal := NewAddMemberSignal(listener.ID)
+  add_member_response := testSend(t, ctx, add_member_signal, listener, group)
+  checkSignal(t, add_member_response, testSuccess)
+
+  testSendACL(t, ctx, listener, nil, []Policy{
+    NewMemberOfPolicy(map[NodeID]Tree{
+      group.ID: nil,
+    }),
+  }, testSuccess)
+}
diff --git a/context.go b/context.go
index b4320d0..68fbbd9 100644
--- a/context.go
+++ b/context.go
@@ -1279,6 +1279,11 @@ func NewContext(db * badger.DB, log Logger) (*Context, error) {
     return nil, err
   }
 
+  err = ctx.RegisterExtension(reflect.TypeOf((*ACLExt)(nil)), ACLExtType, nil)
+  if err != nil {
+    return nil, err
+  }
+
   err = ctx.RegisterPolicy(reflect.TypeOf(MemberOfPolicy{}), MemberOfPolicyType)
   if err != nil {
     return nil, err
@@ -1294,6 +1299,16 @@ func NewContext(db * badger.DB, log Logger) (*Context, error) {
     return nil, err
   }
 
+  err = ctx.RegisterSignal(reflect.TypeOf(ACLTimeoutSignal{}), ACLTimeoutSignalType)
+  if err != nil {
+    return nil, err
+  }
+
+  err = ctx.RegisterSignal(reflect.TypeOf(ACLSignal{}), ACLSignalType)
+  if err != nil {
+    return nil, err
+  }
+
   err = ctx.RegisterSignal(reflect.TypeOf(RemoveMemberSignal{}), RemoveMemberSignalType)
   if err != nil {
     return nil, err
diff --git a/group.go b/group.go
index 3dfa572..77d81c6 100644
--- a/group.go
+++ b/group.go
@@ -40,7 +40,7 @@ func NewRemoveMemberSignal(member_id NodeID) *RemoveMemberSignal {
   }
 }
 
-var GroupReadPolicy = NewAllNodesPolicy(Tree{
+var DefaultGroupPolicy = NewAllNodesPolicy(Tree{
   SerializedType(ReadSignalType): {
     SerializedType(GroupExtType): {
       Hash(FieldNameBase, "members"): nil,
diff --git a/node.go b/node.go
index 7d20bbe..6e28d42 100644
--- a/node.go
+++ b/node.go
@@ -70,18 +70,19 @@ func (q QueuedSignal) String() string {
 
 type PendingACL struct {
   Counter int
+  Responses []ResponseSignal
+
   TimeoutID uuid.UUID
   Action Tree
   Principal NodeID
-  Messages Messages
-  Responses []Signal
+
   Signal Signal
   Source NodeID
 }
 
 type PendingSignal struct {
   Policy uuid.UUID
-  Found bool
+  Timeout uuid.UUID
   ID uuid.UUID
 }
 
@@ -314,10 +315,20 @@ func nodeLoop(ctx *Context, node *Node) error {
           for policy_type, sigs := range(pends) {
             for _, m := range(sigs) {
               msgs = append(msgs, m)
-              node.PendingSignals[m.Signal.ID()] = PendingSignal{policy_type, false, msg.Signal.ID()}
+              timeout_signal := NewTimeoutSignal(m.Signal.ID())
+              node.QueueSignal(time.Now().Add(time.Second), timeout_signal)
+              node.PendingSignals[m.Signal.ID()] = PendingSignal{policy_type, timeout_signal.Id, msg.Signal.ID()}
             }
           }
-          node.PendingACLs[msg.Signal.ID()] = PendingACL{len(msgs), timeout_signal.ID(), msg.Signal.Permission(), princ_id, msgs, []Signal{}, msg.Signal, msg.Source}
+          node.PendingACLs[msg.Signal.ID()] = PendingACL{
+            Counter: len(msgs),
+            TimeoutID: timeout_signal.ID(),
+            Action: msg.Signal.Permission(),
+            Principal: princ_id,
+            Responses: []ResponseSignal{},
+            Signal: msg.Signal,
+            Source: msg.Source,
+          }
           ctx.Log.Logf("policy", "Sending signals for pending ACL: %+v", msgs)
           ctx.Send(msgs)
           continue
@@ -364,54 +375,52 @@ func nodeLoop(ctx *Context, node *Node) error {
     if ok == true {
       info, waiting := node.PendingSignals[response.ResponseID()]
       if waiting == true {
-        if info.Found == false {
-          info.Found = true
-          node.PendingSignals[response.ResponseID()] = info
-          ctx.Log.Logf("pending", "FOUND_PENDING_SIGNAL: %s - %s", node.ID, signal)
-          req_info, exists := node.PendingACLs[info.ID]
-          if exists == true {
-            req_info.Counter -= 1
-            req_info.Responses = append(req_info.Responses, signal)
-
-            idx := -1
-            for i, p := range(node.Policies) {
-              if p.ID() == info.Policy {
-                idx = i
-                break
-              }
+        delete(node.PendingSignals, response.ResponseID())
+        ctx.Log.Logf("pending", "FOUND_PENDING_SIGNAL: %s - %s", node.ID, signal)
+
+        req_info, exists := node.PendingACLs[info.ID]
+        if exists == true {
+          req_info.Counter -= 1
+          req_info.Responses = append(req_info.Responses, response)
+
+          idx := -1
+          for i, p := range(node.Policies) {
+            if p.ID() == info.Policy {
+              idx = i
+              break
             }
-            if idx == -1 {
-              ctx.Log.Logf("policy", "PENDING_FOR_NONEXISTENT_POLICY: %s - %s", node.ID, info.Policy)
+          }
+          if idx == -1 {
+            ctx.Log.Logf("policy", "PENDING_FOR_NONEXISTENT_POLICY: %s - %s", node.ID, info.Policy)
+            delete(node.PendingACLs, info.ID)
+          } else {
+            allowed := node.Policies[idx].ContinueAllows(ctx, req_info, signal)
+            if allowed == Allow {
+              ctx.Log.Logf("policy", "DELAYED_POLICY_ALLOW: %s - %s", node.ID, req_info.Signal)
+              signal = req_info.Signal
+              source = req_info.Source
+              err := node.DequeueSignal(req_info.TimeoutID)
+              if err != nil {
+                ctx.Log.Logf("node", "dequeue error: %s", err)
+              }
               delete(node.PendingACLs, info.ID)
-            } else {
-              allowed := node.Policies[idx].ContinueAllows(ctx, req_info, signal)
-              if allowed == Allow {
-                ctx.Log.Logf("policy", "DELAYED_POLICY_ALLOW: %s - %s", node.ID, req_info.Signal)
-                signal = req_info.Signal
-                source = req_info.Source
-                err := node.DequeueSignal(req_info.TimeoutID)
-                if err != nil {
-                  panic("dequeued a passed signal")
-                }
-                delete(node.PendingACLs, info.ID)
-              } else if req_info.Counter == 0 {
-                ctx.Log.Logf("policy", "DELAYED_POLICY_DENY: %s - %s", node.ID, req_info.Signal)
-                // Send the denied response
-                msgs := Messages{}
-                msgs = msgs.Add(ctx, node.ID, node.Key, NewErrorSignal(req_info.Signal.ID(), "ACL_DENIED"), req_info.Source)
-                err := ctx.Send(msgs)
-                if err != nil {
-                  ctx.Log.Logf("signal", "SEND_ERR: %s", err)
-                }
-                err = node.DequeueSignal(req_info.TimeoutID)
-                if err != nil {
-                  panic("dequeued a passed signal")
-                }
-                delete(node.PendingACLs, info.ID)
-              } else {
-                node.PendingACLs[info.ID] = req_info
-                continue
+            } else if req_info.Counter == 0 {
+              ctx.Log.Logf("policy", "DELAYED_POLICY_DENY: %s - %s", node.ID, req_info.Signal)
+              // Send the denied response
+              msgs := Messages{}
+              msgs = msgs.Add(ctx, node.ID, node.Key, NewErrorSignal(req_info.Signal.ID(), "ACL_DENIED"), req_info.Source)
+              err := ctx.Send(msgs)
+              if err != nil {
+                ctx.Log.Logf("signal", "SEND_ERR: %s", err)
+              }
+              err = node.DequeueSignal(req_info.TimeoutID)
+              if err != nil {
+                panic("dequeued a passed signal")
               }
+              delete(node.PendingACLs, info.ID)
+            } else {
+              node.PendingACLs[info.ID] = req_info
+              continue
             }
           }
         }
diff --git a/policy.go b/policy.go
index c262247..69bd5f9 100644
--- a/policy.go
+++ b/policy.go
@@ -100,6 +100,7 @@ func (policy MemberOfPolicy) ContinueAllows(ctx *Context, current PendingACL, si
   if ok == false {
     return Deny
   }
+  ctx.Log.Logf("group", "member_of_read_result: %+v", sig.Extensions)
 
   group_ext_data, ok := sig.Extensions[GroupExtType]
   if ok == false {
@@ -116,12 +117,12 @@ func (policy MemberOfPolicy) ContinueAllows(ctx *Context, current PendingACL, si
     return Deny
   }
 
-  members, ok := members_if.Interface().(map[NodeID]string)
+  members, ok := members_if.Interface().([]NodeID)
   if ok == false {
     return Deny
   }
 
-  for member := range(members) {
+  for _, member := range(members) {
     if member == current.Principal {
       return policy.NodeRules[sig.NodeID].Allows(current.Action)
     }
diff --git a/serialize.go b/serialize.go
index 9c17076..f760e0f 100644
--- a/serialize.go
+++ b/serialize.go
@@ -83,6 +83,7 @@ var (
   LockableExtType = NewExtType("LOCKABLE")
   GQLExtType      = NewExtType("GQL")
   GroupExtType    = NewExtType("GROUP")
+  ACLExtType      = NewExtType("ACL")
 
   GQLNodeType   = NewNodeType("GQL")
   BaseNodeType  = NewNodeType("BASE")
@@ -102,6 +103,7 @@ var (
   ReadResultSignalType   = NewSignalType("READ_RESULT")
   RemoveMemberSignalType = NewSignalType("REMOVE_MEMBER")
   AddMemberSignalType    = NewSignalType("ADD_MEMBER")
+  ACLSignalType          = NewSignalType("ACL")
 
   MemberOfPolicyType      = NewPolicyType("USER_OF")
   RequirementOfPolicyType = NewPolicyType("REQUIEMENT_OF")
diff --git a/signal.go b/signal.go
index a027963..e6d1c51 100644
--- a/signal.go
+++ b/signal.go
@@ -15,12 +15,12 @@ const (
 )
 
 type TimeoutSignal struct {
-  SignalHeader
+  ResponseHeader
 }
 
-func NewTimeoutSignal() *TimeoutSignal {
+func NewTimeoutSignal(req_id uuid.UUID) *TimeoutSignal {
   return &TimeoutSignal{
-    NewSignalHeader(Direct),
+    NewResponseHeader(req_id, Direct),
   }
 }