No. Unofficially they are open, as they don't close them off. There are posted hours. Usually midnight. It is on the signs at the pools. As long as everyone is quiet and do not disturb sleeping guests security will leave them in the pool.
If they get roudy and noisey and bother the guests in nearby rooms, call security and they will deal with it.
We had this problem one night at the BCV and security cleared the pool and turned off all the lights.