I mean, Walker above pretty much took care of the strange non-dilemma of the OP. If it is consensual, it's not sexual assault.
And why choose 'groping' which generally means clumsy confused touching OR touching sexually without consent?
What's the situation you are concerned about?
You are with someone and they want to be groped, or more likely touched in a way they like.
Well, that's fine. No police come.
You're with someone who doesn't want that, well then you may have a problem. That's in the laws of most countries.
Though whoever these gropers are might want to learn how to touch without groping. I mean, you might as well be good at it.