Some require that there be physical contact and others state that merely revealing genitals and/or naked female breasts is enough to warrant an arrest.  Even that aside, some areas have LE that are so rabid against people having any fun that they'll bust you anyways even if they know a judge will toss the charges, just to be bastards about it.

For those wondering as I did what CFNM is, here's the UD on it.  It does not appear in TER's acronym list, though it probably should.

(still not a lawyer)

LE have the mindset that everyone is guilty and their job is to arrest you, no matter what.  

So good luck with that.