diff --git a/metropolis/proto/ext/BUILD.bazel b/metropolis/proto/ext/BUILD.bazel
new file mode 100644
index 0000000..c93882e
--- /dev/null
+++ b/metropolis/proto/ext/BUILD.bazel
@@ -0,0 +1,24 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
+
+proto_library(
+    name = "ext_proto",
+    srcs = ["authorization.proto"],
+    visibility = ["//visibility:public"],
+    deps = ["@com_google_protobuf//:descriptor_proto"],
+)
+
+go_proto_library(
+    name = "ext_go_proto",
+    importpath = "source.monogon.dev/metropolis/proto/ext",
+    proto = ":ext_proto",
+    visibility = ["//visibility:public"],
+)
+
+go_library(
+    name = "go_default_library",
+    embed = [":ext_go_proto"],
+    importpath = "source.monogon.dev/metropolis/proto/ext",
+    visibility = ["//visibility:public"],
+)