I was formally trespassed 3 months after I abruptly resigned from my job with at a Nevada casino. During those 3 months, I was in that casino many times for gambling, dinners or just to visit people I know. Suddenly one night while watching Monday Night Football, I was called out of the showroom and formally trespassed without explanation. After several months of trying to find out why, I received a letter stating that I was trespassed "based solely upon my actions of the past". NO SPECIFICS OF WHAT "MY ACTIONS OF THE PAST" WERE. Do I have a case for discrimination?

No. Why do YOU think you were banned? Unless you can PROVE it was based on gender, race, something along those lines, you have no case.

Assuming you spend time and money there why would they ban you?