Filter the content

single.php

add_filter( 'the_content', 'cv_the_content_filter' );

function cv_the_content_filter( $content ) {

	$can_user_watch_videos = cv_can_user_watch_videos();

	if ( $can_user_watch_videos !== true ) {

		$content = $can_user_watch_videos;
	} 

	return $content;
}