I mean technically if you are available to answer phone calls or emails, I think we should consider you are "working". I mean it is ridiculous to pay you by the hour at that point but if I didn't have to pay you by the hour, that's the criteria I'd use.

I think I read somewhere that somewhere in France or Germany some city or some department/province said you can't require your employees to promptly respond to emails outside of their work hours (I imagine they don't have "at-will" employment).