"The US State Department demands that passengers are not allowed to congregate in groups around the toilets nor anywhere in the aircraft."
So if you want to use the lav, you call the flight attendant and he/she will give you a number. You then wait to be called in your seat. When it's your turn, you proceed to the lav, use it and then promptly return to your seat, avoiding congregating with other passengers. What could be more simple?
