Second play may not be able to leave view

Hey im makin a top down shooter with a function to drop and add the second player at any moment. The camera is focussed on player 1 and if player 2 is playing he should not be able to leave the view that player 1 is moving around by walking. it's a bit similiar to lego stars wars.

i was thinking about putting walls just outside the edge of the camera view but i think thats not really a good way to do it.

thanks is advance for help.