In laws always visiting unannounced

Hi mommies, I have in laws (husband’s cousins, aunties, uncles, MIL friends) always showing up at the door unannounced. It’s really frustrating. No warning or what so ever, they will just ring the door bell. Husband can’t do anything either. And my MIL is okay with this habit as they all have been doing this for the longest time. Any suggestions on how to face this? Am so tired of this happening over and over again.