A PHP snippet to protect paywalled content (e.g. whitepapers) from being freely accessed by the WordPress REST API

gutenberg-paywalls.php

<?php

function tf_filter_gutenberg_post_types( $args, $post_type ) {
	// Return early - we're not registering the right CPT
	if ( 'whitepaper' !== $post_type ) {
		return $args;
	}

	// Only enable the REST API for users with edit permissions, otherwise
	// explicitly disable it. This prevents other users having access to
	// post content (via the API), which would bypass a paywall.
	$args['show_in_rest'] = current_user_can( 'edit_whitepapers' );

	return $args;
}
add_filter( 'register_post_type_args', 'tf_filter_gutenberg_post_types', 10, 2 );