diff --git a/integration/src/test/scala/org/knora/webapi/e2e/admin/UsersADME2ESpec.scala b/integration/src/test/scala/org/knora/webapi/e2e/admin/UsersADME2ESpec.scala
index 0f9c2f8684..2e2ddd0932 100644
--- a/integration/src/test/scala/org/knora/webapi/e2e/admin/UsersADME2ESpec.scala
+++ b/integration/src/test/scala/org/knora/webapi/e2e/admin/UsersADME2ESpec.scala
@@ -296,6 +296,27 @@ class UsersADME2ESpec
     }
 
     "given a custom Iri" should {
+      "given no credentials in the request when creating a user it must be forbidden" in {
+        val validUserCreationRequest: String =
+          s"""{
+             |    "id": "$customUserIri",
+             |    "username": "userWithCustomIri",
+             |    "email": "userWithCustomIri@example.org",
+             |    "givenName": "a user",
+             |    "familyName": "with a custom Iri",
+             |    "password": "test",
+             |    "status": true,
+             |    "lang": "en",
+             |    "systemAdmin": false
+             |}""".stripMargin
+        val request = Post(
+          baseApiUrl + s"/admin/users",
+          HttpEntity(ContentTypes.`application/json`, validUserCreationRequest)
+        )
+        val response: HttpResponse = singleAwaitingRequest(request)
+        response.status should be(StatusCodes.Forbidden)
+      }
+
       "create a user with the provided custom IRI" in {
         val createUserWithCustomIriRequest: String =
           s"""{
@@ -323,7 +344,7 @@ class UsersADME2ESpec
         val request = Post(
           baseApiUrl + s"/admin/users",
           HttpEntity(ContentTypes.`application/json`, createUserWithCustomIriRequest)
-        )
+        ) ~> addRootUserCredentials()
         val response: HttpResponse = singleAwaitingRequest(request)
 
         response.status should be(StatusCodes.OK)
@@ -359,7 +380,10 @@ class UsersADME2ESpec
              |    "systemAdmin": false
              |}""".stripMargin
 
-        val request                = Post(baseApiUrl + s"/admin/users", HttpEntity(ContentTypes.`application/json`, params))
+        val request = Post(
+          baseApiUrl + s"/admin/users",
+          HttpEntity(ContentTypes.`application/json`, params)
+        ) ~> addRootUserCredentials()
         val response: HttpResponse = singleAwaitingRequest(request)
         response.status should be(StatusCodes.BadRequest)
 
@@ -389,7 +413,7 @@ class UsersADME2ESpec
         val request = Post(
           baseApiUrl + s"/admin/users",
           HttpEntity(ContentTypes.`application/json`, createUserWithApostropheRequest)
-        )
+        ) ~> addRootUserCredentials()
         val response: HttpResponse = singleAwaitingRequest(request)
 
         response.status should be(StatusCodes.OK)
@@ -463,7 +487,11 @@ class UsersADME2ESpec
             text = createUserRequest
           )
         )
-        val request                = Post(baseApiUrl + s"/admin/users", HttpEntity(ContentTypes.`application/json`, createUserRequest))
+        val request = Post(
+          baseApiUrl + s"/admin/users",
+          HttpEntity(ContentTypes.`application/json`, createUserRequest)
+        ) ~> addRootUserCredentials()
+
         val response: HttpResponse = singleAwaitingRequest(request)
 
         response.status should be(StatusCodes.OK)
@@ -513,7 +541,10 @@ class UsersADME2ESpec
             text = createUserRequest
           )
         )
-        val request                = Post(baseApiUrl + s"/admin/users", HttpEntity(ContentTypes.`application/json`, createUserRequest))
+        val request = Post(
+          baseApiUrl + s"/admin/users",
+          HttpEntity(ContentTypes.`application/json`, createUserRequest)
+        ) ~> addRootUserCredentials()
         val response: HttpResponse = singleAwaitingRequest(request)
 
         response.status should be(StatusCodes.BadRequest)
@@ -553,7 +584,10 @@ class UsersADME2ESpec
             text = createUserRequest
           )
         )
-        val request                = Post(baseApiUrl + s"/admin/users", HttpEntity(ContentTypes.`application/json`, createUserRequest))
+        val request = Post(
+          baseApiUrl + s"/admin/users",
+          HttpEntity(ContentTypes.`application/json`, createUserRequest)
+        ) ~> addRootUserCredentials()
         val response: HttpResponse = singleAwaitingRequest(request)
 
         response.status should be(StatusCodes.BadRequest)
diff --git a/webapi/src/main/scala/org/knora/webapi/routing/ApiRoutes.scala b/webapi/src/main/scala/org/knora/webapi/routing/ApiRoutes.scala
index a0d835b5c0..775e32e36a 100644
--- a/webapi/src/main/scala/org/knora/webapi/routing/ApiRoutes.scala
+++ b/webapi/src/main/scala/org/knora/webapi/routing/ApiRoutes.scala
@@ -31,6 +31,7 @@ import org.knora.webapi.slice.admin.api.AdminApiRoutes
 import org.knora.webapi.slice.admin.api.ProjectsEndpointsHandler
 import org.knora.webapi.slice.admin.api.service.ProjectADMRestService
 import org.knora.webapi.slice.admin.domain.service.KnoraProjectRepo
+import org.knora.webapi.slice.common.api.AuthorizationRestService
 import org.knora.webapi.slice.ontology.api.service.RestCardinalityService
 import org.knora.webapi.slice.resourceinfo.api.ResourceInfoRoutes
 import org.knora.webapi.slice.resourceinfo.api.service.RestResourceInfoService
@@ -48,7 +49,7 @@ object ApiRoutes {
    * All routes composed together.
    */
   val layer: URLayer[
-    ActorSystem & AdminApiRoutes & AppConfig & AppRouter & core.State & IriConverter & KnoraProjectRepo & MessageRelay & ProjectADMRestService & ProjectsEndpointsHandler & ResourceInfoRoutes & RestCardinalityService & RestResourceInfoService & routing.Authenticator & SearchApiRoutes & SearchResponderV2 & SipiService & StringFormatter & UsersResponderADM & ValuesResponderV2,
+    ActorSystem & AuthorizationRestService & AdminApiRoutes & AppConfig & AppRouter & core.State & IriConverter & KnoraProjectRepo & MessageRelay & ProjectADMRestService & ProjectsEndpointsHandler & ResourceInfoRoutes & RestCardinalityService & RestResourceInfoService & routing.Authenticator & SearchApiRoutes & SearchResponderV2 & SipiService & StringFormatter & UsersResponderADM & ValuesResponderV2,
     ApiRoutes
   ] =
     ZLayer {
@@ -62,7 +63,7 @@ object ApiRoutes {
         routeData          <- ZIO.succeed(KnoraRouteData(sys.system, router.ref, appConfig))
         runtime <-
           ZIO.runtime[
-            AppConfig & core.State & IriConverter & KnoraProjectRepo & MessageRelay & ProjectADMRestService & RestCardinalityService & RestResourceInfoService & routing.Authenticator & SearchApiRoutes & SearchResponderV2 & SipiService & StringFormatter & UsersResponderADM & ValuesResponderV2
+            AppConfig & AuthorizationRestService & core.State & IriConverter & KnoraProjectRepo & MessageRelay & ProjectADMRestService & RestCardinalityService & RestResourceInfoService & routing.Authenticator & SearchApiRoutes & SearchResponderV2 & SipiService & StringFormatter & UsersResponderADM & ValuesResponderV2
           ]
       } yield ApiRoutesImpl(routeData, adminApiRoutes, resourceInfoRoutes, searchApiRoutes, appConfig, runtime)
     }
@@ -82,7 +83,7 @@ private final case class ApiRoutesImpl(
   searchApiRoutes: SearchApiRoutes,
   appConfig: AppConfig,
   implicit val runtime: Runtime[
-    AppConfig & core.State & IriConverter & KnoraProjectRepo & MessageRelay & ProjectADMRestService & RestCardinalityService & RestResourceInfoService & routing.Authenticator & SearchResponderV2 & SipiService & StringFormatter & UsersResponderADM & ValuesResponderV2
+    AppConfig & AuthorizationRestService & core.State & IriConverter & KnoraProjectRepo & MessageRelay & ProjectADMRestService & RestCardinalityService & RestResourceInfoService & routing.Authenticator & SearchResponderV2 & SipiService & StringFormatter & UsersResponderADM & ValuesResponderV2
   ]
 ) extends ApiRoutes
     with AroundDirectives {
diff --git a/webapi/src/main/scala/org/knora/webapi/routing/admin/UsersRouteADM.scala b/webapi/src/main/scala/org/knora/webapi/routing/admin/UsersRouteADM.scala
index 29e1a15114..0e4da37e7f 100644
--- a/webapi/src/main/scala/org/knora/webapi/routing/admin/UsersRouteADM.scala
+++ b/webapi/src/main/scala/org/knora/webapi/routing/admin/UsersRouteADM.scala
@@ -23,12 +23,13 @@ import org.knora.webapi.routing.RouteUtilADM.getIriUserUuid
 import org.knora.webapi.routing.RouteUtilADM.getUserUuid
 import org.knora.webapi.routing.RouteUtilADM.runJsonRouteZ
 import org.knora.webapi.slice.admin.domain.model.*
+import org.knora.webapi.slice.common.api.AuthorizationRestService
 
 /**
  * Provides an pekko-http-routing function for API routes that deal with users.
  */
 final case class UsersRouteADM()(
-  private implicit val runtime: Runtime[Authenticator & StringFormatter & MessageRelay]
+  private implicit val runtime: Runtime[Authenticator & AuthorizationRestService & StringFormatter & MessageRelay]
 ) {
 
   private val usersBasePath: PathMatcher[Unit] = PathMatcher("admin" / "users")
@@ -58,6 +59,7 @@ final case class UsersRouteADM()(
         val requestTask = for {
           payload <- UserCreatePayloadADM.make(apiRequest).mapError(BadRequestException(_)).toZIO
           r       <- getUserUuid(ctx)
+          _       <- AuthorizationRestService.ensureSystemAdmin(r.user)
         } yield UserCreateRequestADM(payload, r.user, r.uuid)
         runJsonRouteZ(requestTask, ctx)
       }