It's actually illegal to form "Men's Clubs" in the US now. This is one of the decisions that enforces it: https://www.nytimes.com/1987/05/05/us/high-court-rules-that-rotary-clubs-must-admit-women.html The only way around that is a non-advertised, BYOB/PotLuck style event on private property. As long as money or sevices aren't being traded, it's cool to have a "Guy's night in" kinda thing, but an openly exclusive club is illegal. Unless it's a women's only gym or fitness studio, etc. Then the law doesn't apply.