Ah, yes - the well known right to show your butt crack anywhere you want.
Which part of the Bill of Rights covered that, so to speak?
This is a state law, so you are on the wrong channel. The same clothes that are worn at the beach would be outlawed at the mall??? Or are you saying that I can go to the mall in a bathing suit as long as I'm not wearing a pair of droopy pants on top of them?
Since you asked, it would be the 1st amendment. It's interpreted to allow for the right to freedom of expression.