I tried posting this on McGriff's, but I didn't get any bites. I believe this is a foul, but I can't find a reference:

A punts from the A-20. Flyer A88 gets blocked and is forced OOB by B24 at the A-30. A88 is now in the coaches area and is trying reverse his momentum so that he can return to the field. B24 then blocks A88 who is 3 to 4 yards OOB at the A-40. B32 fair catches the ball at the B-40.

Rule references please.

You can't block someone who is out of bounds. I cannot find the rule right now - not enough coffee. I'll find it though.