Yes, it's private property and they can ban any person with or without reason. They don't have to defend it. They don't need a reason. They don't like you, so you're not allowed back. That's it. It's really that simple.
It's private property, just like your home is your private property. If you say someone isn't allowed back into your home, then that's it. You don't need a reason. You don't need evidence. You don't need to defend it. That's your right.
I hate to be the one to break it to you, but getting the casino to reverse the ban is no small feat. The 1 year thing is just a random number that the security guard told you to shut you up. You've been banned for life and can appeal in a year? Yeah, that sounds like your appeal is going to be laughed at.
Again, let's go back to the analogy of private property. Let's think about your home.
Suppose you had a messy breakup with an ex-boyfriend. You tell him that you hate him, that you never want to see him again, and that he's never allowed to step foot in your house again. Then you tell him that after a year, he can beg for forgiveness and you might reconsider. Think about it: after a year passes, will you really let him back into your home? Absolutely no chance, right?
To answer your question, "Are we really banned for a year?" The answer is no. You're not banned for a year. You're banned for life.
To answer your question, "Can we contact security and appeal sooner?" Sure, you can call. But you have as much chance of being allowed back into Encore as your ex-boyfriend has a chance of being allowed back in your home. It's a pretty worthless endeavor, right?
Trespass laws in Nevada casinos are a serious thing. This was no empty threat. It's called being 86'd. If it was an empty threat, uncommon, or not a big deal, there wouldn't be a nickname for it. If it wasn't a big deal, there wouldn't be so much literature about it on the internet.
It's common. It's real. And it's permanent.
https://www.youtube.com/watch?v=11xHyqRzeHk https://www.shouselaw.com/nevada/trespass.html https://forumserver.twoplustwo.com/108/las-vegas-lifestyle/possible-get-reallowed-into-casino-1299434/?s=d89b6c2795cba40f05672190e46037d2