Only show booking form to group members

I know you can limit bookings to group members only by making the event private, but this shows no activity for the group to visitors.

I was wondering if it is possible to not show the booking form on a public event, if the user is not a member of the group?

I was looking at:

/events-manager/templates/placeholders/bookingform.php

Could a filter be added to this piece of code?

//if user is logged out, check for member tickets that might be available, since we should ask them to log in instead of saying 'bookings closed'
if( !$is_open && !is_user_logged_in() && $EM_Event->get_bookings()->is_open(true) ){
    $is_open = true;
    $can_book = false;
	$show_tickets = get_option('dbem_bookings_tickets_show_unavailable') && get_option('dbem_bookings_tickets_show_member_tickets');
}

Any other suggestions would be welcome.