diff --git a/changelog.d/6214.misc b/changelog.d/6214.misc
new file mode 100644
index 000000000..c3fd04d0d
--- /dev/null
+++ b/changelog.d/6214.misc
@@ -0,0 +1 @@
+Remove some unused event-auth code.
diff --git a/scripts-dev/check_auth.py b/scripts-dev/check_auth.py
deleted file mode 100644
index 2a1c5f39d..000000000
--- a/scripts-dev/check_auth.py
+++ /dev/null
@@ -1,58 +0,0 @@
-from __future__ import print_function
-
-import argparse
-import itertools
-import json
-import sys
-
-from mock import Mock
-
-from synapse.api.auth import Auth
-from synapse.events import FrozenEvent
-
-
-def check_auth(auth, auth_chain, events):
-    auth_chain.sort(key=lambda e: e.depth)
-
-    auth_map = {e.event_id: e for e in auth_chain}
-
-    create_events = {}
-    for e in auth_chain:
-        if e.type == "m.room.create":
-            create_events[e.room_id] = e
-
-    for e in itertools.chain(auth_chain, events):
-        auth_events_list = [auth_map[i] for i, _ in e.auth_events]
-
-        auth_events = {(e.type, e.state_key): e for e in auth_events_list}
-
-        auth_events[("m.room.create", "")] = create_events[e.room_id]
-
-        try:
-            auth.check(e, auth_events=auth_events)
-        except Exception as ex:
-            print("Failed:", e.event_id, e.type, e.state_key)
-            print("Auth_events:", auth_events)
-            print(ex)
-            print(json.dumps(e.get_dict(), sort_keys=True, indent=4))
-            # raise
-        print("Success:", e.event_id, e.type, e.state_key)
-
-
-if __name__ == "__main__":
-    parser = argparse.ArgumentParser()
-
-    parser.add_argument(
-        "json", nargs="?", type=argparse.FileType("r"), default=sys.stdin
-    )
-
-    args = parser.parse_args()
-
-    js = json.load(args.json)
-
-    auth = Auth(Mock())
-    check_auth(
-        auth,
-        [FrozenEvent(d) for d in js["auth_chain"]],
-        [FrozenEvent(d) for d in js.get("pdus", [])],
-    )
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index f29bce560..60e99e466 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -97,8 +97,6 @@ class EventTypes(object):
 
 class RejectedReason(object):
     AUTH_ERROR = "auth_error"
-    REPLACED = "replaced"
-    NOT_ANCESTOR = "not_ancestor"
 
 
 class RoomCreationPreset(object):
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 6ee621666..5b22a39b7 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -878,44 +878,6 @@ class FederationClient(FederationBase):
             third_party_instance_id=third_party_instance_id,
         )
 
-    @defer.inlineCallbacks
-    def query_auth(self, destination, room_id, event_id, local_auth):
-        """
-        Params:
-            destination (str)
-            event_it (str)
-            local_auth (list)
-        """
-        time_now = self._clock.time_msec()
-
-        send_content = {"auth_chain": [e.get_pdu_json(time_now) for e in local_auth]}
-
-        code, content = yield self.transport_layer.send_query_auth(
-            destination=destination,
-            room_id=room_id,
-            event_id=event_id,
-            content=send_content,
-        )
-
-        room_version = yield self.store.get_room_version(room_id)
-        format_ver = room_version_to_event_format(room_version)
-
-        auth_chain = [event_from_pdu_json(e, format_ver) for e in content["auth_chain"]]
-
-        signed_auth = yield self._check_sigs_and_hash_and_fetch(
-            destination, auth_chain, outlier=True, room_version=room_version
-        )
-
-        signed_auth.sort(key=lambda e: e.depth)
-
-        ret = {
-            "auth_chain": signed_auth,
-            "rejects": content.get("rejects", []),
-            "missing": content.get("missing", []),
-        }
-
-        return ret
-
     @defer.inlineCallbacks
     def get_missing_events(
         self,
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 482a101c0..7b1840814 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -381,17 +381,6 @@ class TransportLayerClient(object):
 
         return content
 
-    @defer.inlineCallbacks
-    @log_function
-    def send_query_auth(self, destination, room_id, event_id, content):
-        path = _create_v1_path("/query_auth/%s/%s", room_id, event_id)
-
-        content = yield self.client.post_json(
-            destination=destination, path=path, data=content
-        )
-
-        return content
-
     @defer.inlineCallbacks
     @log_function
     def query_client_keys(self, destination, query_content, timeout):
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 50fc0fde2..57f661f16 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -2181,103 +2181,10 @@ class FederationHandler(BaseHandler):
 
             auth_events.update(new_state)
 
-            different_auth = event_auth_events.difference(
-                e.event_id for e in auth_events.values()
-            )
-
             yield self._update_context_for_auth_events(
                 event, context, auth_events, event_key
             )
 
-        if not different_auth:
-            # we're done
-            return
-
-        logger.info(
-            "auth_events still refers to events which are not in the calculated auth "
-            "chain after state resolution: %s",
-            different_auth,
-        )
-
-        # Only do auth resolution if we have something new to say.
-        # We can't prove an auth failure.
-        do_resolution = False
-
-        for e_id in different_auth:
-            if e_id in have_events:
-                if have_events[e_id] == RejectedReason.NOT_ANCESTOR:
-                    do_resolution = True
-                    break
-
-        if not do_resolution:
-            logger.info(
-                "Skipping auth resolution due to lack of provable rejection reasons"
-            )
-            return
-
-        logger.info("Doing auth resolution")
-
-        prev_state_ids = yield context.get_prev_state_ids(self.store)
-
-        # 1. Get what we think is the auth chain.
-        auth_ids = yield self.auth.compute_auth_events(event, prev_state_ids)
-        local_auth_chain = yield self.store.get_auth_chain(auth_ids, include_given=True)
-
-        try:
-            # 2. Get remote difference.
-            try:
-                result = yield self.federation_client.query_auth(
-                    origin, event.room_id, event.event_id, local_auth_chain
-                )
-            except RequestSendFailed as e:
-                # The other side isn't around or doesn't implement the
-                # endpoint, so lets just bail out.
-                logger.info("Failed to query auth from remote: %s", e)
-                return
-
-            seen_remotes = yield self.store.have_seen_events(
-                [e.event_id for e in result["auth_chain"]]
-            )
-
-            # 3. Process any remote auth chain events we haven't seen.
-            for ev in result["auth_chain"]:
-                if ev.event_id in seen_remotes:
-                    continue
-
-                if ev.event_id == event.event_id:
-                    continue
-
-                try:
-                    auth_ids = ev.auth_event_ids()
-                    auth = {
-                        (e.type, e.state_key): e
-                        for e in result["auth_chain"]
-                        if e.event_id in auth_ids or event.type == EventTypes.Create
-                    }
-                    ev.internal_metadata.outlier = True
-
-                    logger.debug(
-                        "do_auth %s different_auth: %s", event.event_id, e.event_id
-                    )
-
-                    yield self._handle_new_event(origin, ev, auth_events=auth)
-
-                    if ev.event_id in event_auth_events:
-                        auth_events[(ev.type, ev.state_key)] = ev
-                except AuthError:
-                    pass
-
-        except Exception:
-            # FIXME:
-            logger.exception("Failed to query auth chain")
-
-        # 4. Look at rejects and their proofs.
-        # TODO.
-
-        yield self._update_context_for_auth_events(
-            event, context, auth_events, event_key
-        )
-
     @defer.inlineCallbacks
     def _update_context_for_auth_events(self, event, context, auth_events, event_key):
         """Update the state_ids in an event context after auth event resolution,
@@ -2444,15 +2351,6 @@ class FederationHandler(BaseHandler):
 
             reason_map[e.event_id] = reason
 
-            if reason == RejectedReason.AUTH_ERROR:
-                pass
-            elif reason == RejectedReason.REPLACED:
-                # TODO: Get proof
-                pass
-            elif reason == RejectedReason.NOT_ANCESTOR:
-                # TODO: Get proof.
-                pass
-
         logger.debug("construct_auth_difference returning")
 
         return {