Can a Hotel give a guest a ten o'clock curfew if older than 18 years old?

I've been staying at a hotel for a few weeks now and had a few friends come over to chit chat, The time my friends arrived was after 10 o'clock p.m. Shortly after arriving there was a knock at my door, it was the hotel manager, she came in very rudely and had said no one is allowed at the hotel after 10 and if my friends didnt leave right then she would call the poice. My friends immidiatly got up and walked outside to find out she had already called the police. My friends got citations for tresping. The hotel had not mentioned anything about the ten o'clock rule when i checked in and i have never read anything at the hotel stating this. Can a hotel really give curfews to guest's older then the age of 18?