When you enter the club you must be in Civilian clothing. When you go outside to smoke or vape you are to be presentable and have a top and bottom piece on; This includes underwear with a t-shirt, diaper and t-shirt, leather gear that covers both the crotch and butt, frocks, sissy clothes, civilian clothing, etc. Shoes are optional and suggest wearing shoes outside.
When inside you are, literally, free to wear whatever you like. Clothed or unclothed; It is your choice!