diff --git a/sapient_apex_server/translator/proto_to_proto_translator.py b/sapient_apex_server/translator/proto_to_proto_translator.py
index 609d2a1..f93c5af 100644
--- a/sapient_apex_server/translator/proto_to_proto_translator.py
+++ b/sapient_apex_server/translator/proto_to_proto_translator.py
@@ -166,13 +166,42 @@ def _registration_translate_v2_to_v1(message_dict: dict) -> bool:
     # value back from CommandType enum instead
     mode_definitions = registration_dict.get("mode_definition", [])
 
+    v2_only_command_types = {
+        "COMMAND_TYPE_MOVE_TO",
+        "COMMAND_TYPE_PATROL",
+        "COMMAND_TYPE_FOLLOW",
+    }
+    v2_only_region_types = {
+        "REGION_TYPE_MOBILE_NODE_NO_GO_AREA",
+        "REGION_TYPE_MOBILE_NODE_GO_AREA",
+    }
+
     for mode_definition in mode_definitions:
         _convert_repeated_to_single(mode_definition, "detection_definition")
         _convert_single_to_repeated(mode_definition, "task")
 
+        # Extensible taxonomy docking was introduced in V2 and has no V1 representation.
+        detection_definition = mode_definition.get("detection_definition", {})
+        detection_classes = detection_definition.get("detection_class_definition", [])
+        for detection_class in detection_classes:
+            _remove_fields(detection_class, ["taxonomy_dock_definition"])
+
         tasks = mode_definition.get("task", [])
         for task in tasks:
+            region_definition = task.get("region_definition", {})
+            region_types = region_definition.get("region_type", [])
+            region_types[:] = [
+                region_type
+                for region_type in region_types
+                if region_type not in v2_only_region_types
+            ]
+
             commands = task.get("command", [])
+            # Mobile-node commands were introduced in V2. Drop these capability declarations
+            # when downgrading because the V1 command enum cannot represent them.
+            commands[:] = [
+                command for command in commands if command.get("type") not in v2_only_command_types
+            ]
             for command in commands:
                 if "type" in command:
                     # Get the string representation of the type enum
diff --git a/tests/test_proto_to_proto_translator.py b/tests/test_proto_to_proto_translator.py
new file mode 100644
index 0000000..459499b
--- /dev/null
+++ b/tests/test_proto_to_proto_translator.py
@@ -0,0 +1,67 @@
+#
+# Copyright (c) 2019-2024 Roke Manor Research Ltd
+#
+
+from google.protobuf.json_format import MessageToDict, ParseDict
+
+from sapient_apex_server.translator.proto_to_proto_translator import translate_v2_to_v1
+from sapient_msg.bsi_flex_335_v2_0.sapient_message_pb2 import SapientMessage
+
+
+def test_v2_registration_downgrade_omits_v2_only_taxonomy_and_commands():
+    message = ParseDict(
+        {
+            "registration": {
+                "icd_version": "BSI Flex 335 v2.0",
+                "mode_definition": [
+                    {
+                        "detection_definition": [
+                            {
+                                "detection_class_definition": [
+                                    {
+                                        "taxonomy_dock_definition": [
+                                            {
+                                                "Dock_class_namespace": "sapient_core",
+                                                "Dock_class": "Land Vehicle.2 Wheels.Other",
+                                            }
+                                        ]
+                                    }
+                                ]
+                            }
+                        ],
+                        "task": {
+                            "region_definition": {
+                                "region_type": [
+                                    "REGION_TYPE_AREA_OF_INTEREST",
+                                    "REGION_TYPE_MOBILE_NODE_NO_GO_AREA",
+                                    "REGION_TYPE_MOBILE_NODE_GO_AREA",
+                                ]
+                            },
+                            "command": [
+                                {"type": "COMMAND_TYPE_MOVE_TO"},
+                                {"type": "COMMAND_TYPE_PATROL"},
+                                {"type": "COMMAND_TYPE_FOLLOW"},
+                                {"type": "COMMAND_TYPE_LOOK_AT"},
+                            ]
+                        },
+                    }
+                ],
+            }
+        },
+        SapientMessage(),
+    )
+
+    downgraded = translate_v2_to_v1(message)
+    registration = MessageToDict(downgraded, preserving_proto_field_name=True)["registration"]
+
+    assert registration["icd_version"] == "BSI Flex 335 v1.0"
+    detection_definition = registration["mode_definition"][0]["detection_definition"]
+    detection_class = detection_definition["detection_class_definition"][0]
+    assert "taxonomy_dock_definition" not in detection_class
+
+    task = registration["mode_definition"][0]["task"][0]
+    assert task["region_definition"]["region_type"] == ["REGION_TYPE_AREA_OF_INTEREST"]
+
+    commands = task["command"]
+    assert [command["type"] for command in commands] == ["COMMAND_TYPE_LOOK_AT"]
+    assert commands[0]["name"] == "LookAt"