Touching my friend

If she sees it in fun, no problem. If not, you do qualify as a creeper and she should either avoid you or smack you upside the face next time. My female friend and business associate, who admittedly had a great ass (especially in jeans..), was ok and saw it as fun when I'd smack or grope her ass, but, during a function we went to, when one of the creepier business group guys gave her a quick-slap as she leaned over a table, she gave him the verbal beat-down about not touching her, do it again and your hand will be up your own ass and down your throat..Just killing him. And all he really did was a quick, flat-hand smack.

I've grabbed and groped that ass of hers tons of times, on the road, at client's locations, even the night we went out for her birthday. She's fine with me doing it, but not other, creepy guys.

Legally yes

The trick is to make it not look like an accident.

Touching by accident might be excused, but multiple times? You're a fucking creep.