diff --git a/eea/volto/policy/overrides.zcml b/eea/volto/policy/overrides.zcml
index fa819e4..56ca04b 100644
--- a/eea/volto/policy/overrides.zcml
+++ b/eea/volto/policy/overrides.zcml
@@ -3,19 +3,19 @@
   xmlns:zcml="http://namespaces.zope.org/zcml"
   xmlns:browser="http://namespaces.zope.org/browser">
 
-    <include file="restapi/overrides.zcml" />
+  <include file="restapi/overrides.zcml" />
 
-    <configure package="zmi.styles">
-        <browser:resourceDirectory
-            name="zmi"
-            directory="resources"
-            permission="zope.Public" />
-    </configure>
+  <configure package="zmi.styles">
+    <browser:resourceDirectory
+      name="zmi"
+      directory="resources"
+      permission="zope.Public" />
+  </configure>
 
   <utility
     factory=".vocabularies.principals.UsersFactory"
     name="plone.app.vocabularies.Users"
-    />
+  />
 
   <adapter
     factory=".indexers.hasPreviewImage"
diff --git a/eea/volto/policy/restapi/services/breadcrumbs/get.py b/eea/volto/policy/restapi/services/breadcrumbs/get.py
index f170b92..0faea1e 100644
--- a/eea/volto/policy/restapi/services/breadcrumbs/get.py
+++ b/eea/volto/policy/restapi/services/breadcrumbs/get.py
@@ -4,12 +4,13 @@
 from zope.component import adapter
 from zope.interface import implementer
 from zope.interface import Interface
-from plone.restapi.interfaces import IExpandableElement, IPloneRestapiLayer
+from plone.restapi.interfaces import IExpandableElement
 from plone.restapi.services.breadcrumbs.get import Breadcrumbs
+from eea.volto.policy.interfaces import IEeaVoltoPolicyLayer
 
 
 @implementer(IExpandableElement)
-@adapter(Interface, IPloneRestapiLayer)
+@adapter(Interface, IEeaVoltoPolicyLayer)
 class EEABreadcrumbs(Breadcrumbs):
     """EEA Breadcrumbs"""
 
diff --git a/eea/volto/policy/vocabularies/principals.py b/eea/volto/policy/vocabularies/principals.py
index b0a2d50..f8304ec 100644
--- a/eea/volto/policy/vocabularies/principals.py
+++ b/eea/volto/policy/vocabularies/principals.py
@@ -1,9 +1,14 @@
 """Vocabulary for users."""
 
-# Plone imports
 from plone import api
 from plone.app.vocabularies.principals import UsersFactory as BaseUsersFactory
-from plone.app.vocabularies.principals import PrincipalsVocabulary
+from plone.app.vocabularies.principals import (
+    PrincipalsVocabulary,
+    SOURCES,
+    _get_acl_users,
+    # merge_principal_infos,
+    token_from_principal_info,
+)
 from plone.restapi.serializer.vocabularies import SerializeTermToJson
 from plone.restapi.interfaces import ISerializeToJson
 
@@ -15,6 +20,57 @@
 
 # CMFCore imports
 from Products.CMFCore.utils import getToolByName
+from zope.globalrequest import getRequest
+
+_USER_SEARCH_UID = {
+    "search": "searchUsers",
+    # Hint: The fullname search is provided i.e. in IUserEnumeration of
+    # the property plugin in PlonePAS.
+    "searchattr": "uid",
+    "searchargs": {"sort_by": "fullname"},
+    "many": "plone.many_users",
+}
+
+SOURCES["user"]["searches"] += [_USER_SEARCH_UID]
+SOURCES["principal"]["searches"] += [_USER_SEARCH_UID]
+
+
+def merge_principal_infos(infos, acl_users, prefix=False):
+    info = infos[0]
+    if len(infos) > 1:
+        principal_types = {
+            info["principal_type"] for info in infos if info["principal_type"]
+        }
+        if len(principal_types) > 1:
+            # Principals with the same ID but different types. Should not
+            # happen.
+            raise ValueError("Principal ID not unique: {}".format(info["id"]))
+        if not info["title"]:
+            for candidate in infos:
+                if candidate["title"]:
+                    info["title"] = candidate["title"]
+                    break
+
+    if (
+        info.get("pluginid", "") == "pasldap"
+        and info.get("principal_type", "") == "user"
+        and info.get("title", None) == info.get("id", "")
+    ):
+        user = acl_users.getUserById(info["id"])
+        info["title"] = user.getProperty("fullname")
+    return info
+
+
+def unique_terms(objects):
+    unique_objects = []
+    seen_values = set()
+
+    for obj in objects:
+        if obj.value not in seen_values:
+            unique_objects.append(obj)
+            seen_values.add(obj.value)
+
+    return unique_objects
 
 
 class SimpleUserTerm(SimpleTerm):
@@ -24,6 +80,8 @@ class SimpleUserTerm(SimpleTerm):
 class UsersFactory(BaseUsersFactory):
     """Factory creating a UsersVocabulary"""
 
+    _needs_search = False
+
     @property
     def items(self):
         """Return a list of users"""
@@ -46,11 +104,67 @@ def items(self):
             simpleTerm.email = email
             yield simpleTerm
 
+    def should_search(self, query):
+        if self._needs_search:
+            return True
+
+        return super().should_search(query)
+
     def __call__(self, *args, **kwargs):
+        request = getRequest()
+        tokens = request.form.get("tokens", None)
+        if tokens:
+            self._needs_search = True
+            return self.original_tweaked__call__(*args, query=tokens)
+
         vocabulary = PrincipalsVocabulary(list(self.items))
         vocabulary.principal_source = self.source
         return vocabulary
 
+    def original_tweaked__call__(self, context, query=""):
+        if not self.should_search(query):
+            vocabulary = PrincipalsVocabulary([])
+            vocabulary.principal_source = self.source
+            return vocabulary
+
+        acl_users = _get_acl_users()
+        cfg = SOURCES[self.source]
+
+        def term_triples():
+            """Generator for term triples (value, token, name)"""
+            for search_cfg in cfg["searches"]:
+                search = getattr(acl_users, search_cfg["search"])
+                searchargs = search_cfg["searchargs"].copy()
+                searchargs[search_cfg["searchattr"]] = query
+                infotree = {}
+                for info in search(**searchargs):
+                    infotree.setdefault(info["id"], {}).setdefault(
+                        info["principal_type"], []
+                    ).append(info)
+
+                for principal_id, types_infos in infotree.items():
+                    if len(types_infos) > 1 and not cfg["prefix"]:
+                        raise ValueError(f"Principal ID not unique: {principal_id}")
+                    for principal_type, principal_infos in types_infos.items():
+                        if principal_type == "user":
+                            pass
+                        value = principal_id
+                        info = merge_principal_infos(principal_infos, acl_users)
+                        if cfg["prefix"]:
+                            value = "{}:{}".format(info["principal_type"], value)
+                        token = token_from_principal_info(info, prefix=cfg["prefix"])
+                        yield (value, token, info["title"])
+
+        terms = unique_terms(
+            [
+                SimpleTerm(*term_triple)
+                for term_triple in filter(self.use_principal_triple, term_triples())
+            ]
+        )
+        vocabulary = PrincipalsVocabulary(terms)
+        vocabulary.principal_source = self.source
+        return vocabulary
+
 
 @implementer(ISerializeToJson)
 @adapter(SimpleUserTerm, Interface)