So I know this is probably a stupid question that I SHOULD know the answer to, but I thought I would pose it and see what people thought:

I have a student who wishes to do a little refresh flight training. He has a SEL/MEL/IRA and wants to get a little flight training in before we do his BFR so he can get back up to speed. He was wondering if it would be possible, on some of the cross country training flights, to fly to a location, drop him off, and have me fly the aircraft back solo. Is this legal? Or does it fall under and illegal commercial operation? I have been banging my head against the wall on this one, and thought I'd ask some advice. Thanks in advance.