is it legal to bring Cuban cigars across from mexico?
No, but chances are any Cuban cigar purchased in Mexico is going to be a knock off fake so in reality it's not even a cuban. There are only a handfull of legit resellers name La Casa Del habanos that are ran by the Cuban distribution company. Problem is there was an asshole that worked at the one in TJ who stole from people years back. You'd grab a legit box of montes off of the shelf, go to the cash and pay and as he went to put the box in a bag, he'd pull and old switcheroo and grab a fake box he brought in and put it in the bag. Most loser americans didn't know the diff until he tried to ripoff a man in the know and they busted his ass.
Sorry to tell you that 99% of "cuban" cigars sold in mexico are knock offs.
Just check out this site.
www.justfakes.com. You can litteraly buy a $10 box of cigars and turn them into a $400 dollar box.