Broadcast

The snippet below shows how to hook into the threewp_broadcast_get_user_writable_blogs action / filter to remove access to a blog for a specific user, in this case user #1.

/**
	@brief		Remove access to one or more blogs for a specific user.
	@since		2017-05-09 10:16:22
**/
function my_threewp_broadcast_get_user_writable_blogs( $action )
{
	// We want to modify access only for a specific user.
	if ( $action->user_id != 1 )
		return;

	// And we want to remove access to blog # 81
	$action->blogs->forget( 81 );
}
// Broadcast fills the blog list at prio 100, so use a higher number.
add_action( 'threewp_broadcast_get_user_writable_blogs', 'my_threewp_broadcast_get_user_writable_blogs', 200 );