In my books it states that we can't do any removal options before September 1.
But in the mean time, try bat houses somewhere close by. This will give the little critters another roasting option other than the barn. Then come September, harass them into leaving. Lights on at night, brushing them off their perch with a broom or mop, hang a fake snake or two in the rafters, use noise makers to keep them upset, maybe even a radio left playing.
Fake snake.... That may be a stupid idea seeing as how bats have SUCH good eyesight.
But... What the hey? It just might work.