diff --git a/lib/load.php b/lib/load.php
index cb6f3c5cee300f..6e8f9a6e101c86 100644
--- a/lib/load.php
+++ b/lib/load.php
@@ -26,7 +26,6 @@
 
 require dirname( __FILE__ ) . '/client-assets.php';
 require dirname( __FILE__ ) . '/i18n.php';
-require dirname( __FILE__ ) . '/register.php';
 require dirname( __FILE__ ) . '/demo.php';
 require dirname( __FILE__ ) . '/widgets-page.php';
 
diff --git a/lib/register.php b/lib/register.php
deleted file mode 100644
index 91ef3ee26e9aa4..00000000000000
--- a/lib/register.php
+++ /dev/null
@@ -1,86 +0,0 @@
-<?php
-/**
- * Initialization and wp-admin integration for the Gutenberg editor plugin.
- *
- * @package gutenberg
- */
-
-if ( ! defined( 'ABSPATH' ) ) {
-	die( 'Silence is golden.' );
-}
-
-/**
- * Return whether the post can be edited in Gutenberg and by the current user.
- *
- * @since 0.5.0
- * @deprecated 5.1.0 use_block_editor_for_post
- *
- * @param int|WP_Post $post Post ID or WP_Post object.
- * @return bool Whether the post can be edited with Gutenberg.
- */
-function gutenberg_can_edit_post( $post ) {
-	_deprecated_function( __FUNCTION__, '5.1.0', 'use_block_editor_for_post' );
-
-	require_once ABSPATH . 'wp-admin/includes/post.php';
-	return use_block_editor_for_post( $post );
-}
-
-/**
- * Return whether the post type can be edited in Gutenberg.
- *
- * Gutenberg depends on the REST API, and if the post type is not shown in the
- * REST API, then the post cannot be edited in Gutenberg.
- *
- * @since 1.5.2
- * @deprecated 5.1.0 use_block_editor_for_post_type
- *
- * @param string $post_type The post type.
- * @return bool Whether the post type can be edited with Gutenberg.
- */
-function gutenberg_can_edit_post_type( $post_type ) {
-	_deprecated_function( __FUNCTION__, '5.1.0', 'use_block_editor_for_post_type' );
-
-	require_once ABSPATH . 'wp-admin/includes/post.php';
-	return use_block_editor_for_post_type( $post_type );
-}
-
-/**
- * Injects a hidden input in the edit form to propagate the information that classic editor is selected.
- *
- * @since 1.5.2
- * @deprecated 5.1.0
- */
-function gutenberg_remember_classic_editor_when_saving_posts() {
-	_deprecated_function( __FUNCTION__, '5.1.0' );
-}
-
-/**
- * Appends a query argument to the redirect url to make sure it gets redirected to the classic editor.
- *
- * @since 1.5.2
- * @deprecated 5.1.0
- *
- * @param string $url Redirect url.
- * @return string Redirect url.
- */
-function gutenberg_redirect_to_classic_editor_when_saving_posts( $url ) {
-	_deprecated_function( __FUNCTION__, '5.1.0' );
-
-	return $url;
-}
-
-/**
- * Appends a query argument to the edit url to make sure it is redirected to
- * the editor from which the user navigated.
- *
- * @since 1.5.2
- * @deprecated 5.1.0
- *
- * @param string $url Edit url.
- * @return string Edit url.
- */
-function gutenberg_revisions_link_to_editor( $url ) {
-	_deprecated_function( __FUNCTION__, '5.1.0' );
-
-	return $url;
-}