Customs and Border Patrol just about didn’t let me back into the country when I went to Quebec.
They were rummaging through everything I had and were asking me all sorts of questions about why I went to Quebec City.
I told them I could have stayed at home if I wanted to buy drugs.
They didn’t like that too much.
But seriously...if you're a citizen,or have a Green Card,they have to let you in.Of course they can arrest you for certain things but they can't keep you from entering.
Anytime you get sarcastic with CBP personnel you’ll be stopped and “corrected”.
I’ve seen it many times with Gringos.