Author Remove Permission

Hi should this be working correctly to make authors posts require approval?

function return_publish_permissions() {
$user = get_role( 'author' );
$user->add_cap( 'publish_posts' );
}
register_deactivation_hook( __FILE__, 'return_publish_permissions' );

function take_away_publish_permissions() {
$user = new WP_User(5);
$user->add_cap('publish_posts',false);
}
register_activation_hook( __FILE__, 'take_away_publish_permissions' );

Doesn't work, quite annoying not sure where im going wrong.