Restrict Access filters for WordPress Blocks

wclancpa-2019-block-access-filter.php

<?php

function my_restrict_post_filter( $use_block_editor, $post ) {
	$author = get_userdata( $post->post_author );
	if ( 'pento' === $author->user_login ) {
		return (bool) random_int( 0, 1 );
	}

	return $use_block_editor;
}
add_filter( 'use_block_editor_for_post', 'my_restrict_post_filter', 10, 2 );

function my_restrict_post_type_filter( $use_block_editor, $post_type ) {
	if ( 'my_mystical_post_type' === $post_type ) {
		return false;
	}

	return $use_block_editor;
}
add_filter( 'use_block_editor_for_post_type', 'my_restrict_post_type_filter', 10, 2 );

// Block Filter reference
// https://wordpress.stackexchange.com/questions/308021/add-custom-class-to-core-blocks-in-gutenberg?answertab=active#tab-top