Are you only banned from gambling, or are you banned from entering as well?

Gambling. It would be a game ender if you couldn't enter the casino at all.

Thank you. =]

Are there any vanilla methods to get unbanned from gambling?

I have a feeling the developers put these limits in the game simply to avoid lawsuits of people claiming New Vegas made them compulsive gamblers by making it seem hip and cool to fritter away all their money on roulette.

More likely it's in because above average luck characters can get more caps than god from gambling, rendering any economic difficulty moot. And because that's what a real casino would do if you're winning ridiculous amounts with no hint of stopping.

I could vouch for this considering I got over 40,000 caps with a 9 luck character from all three casinos. Of course, I was banned. Never got that achievement :[

I doubt that is the reason. If so they might have balanced Caravan better. You can get more caps than god playing THAT because it's not luck based, and it's not hard to guarantee a win every single time you play it.

I have 500/0 Wins/Losses right now because I know the trick of Caravan.

In a real casino, though, the only time you would be winning that much consistently, is if you were cheating or counting cards. While counting cards isn't illegal, they still don't like it (for obvious reasons). Though the only time I got kicked out of a casino IRL was when I got really drunk and accidentally busted a slot machine at the Palace (pulled lever too hard, it snapped off )

There's no real justification for banning from Caravan, though. Kicking out people who constantly win large amounts (under presumption of hidden cheating) is not abnormal for Casinos. It is abnormal for guys sitting around tables at home placing wagers.

Nothing to do with being kicked out (how can a random wandering caravaner kick me out? lol) but more to do with how you win and how the AI plays. If the AI used face cards against you, or you weren't allowed to discard things, or you can only have a set number of each type of card in your deck... All those things would balance it more to make you actually need to play the game wisely and not just instawin because of bad balance.