Do your professors have a "if you leave the cl, don't come back" rule?

Most professors don't care if you leave and come back, but a bathroom break is really the only excuse for this. You should NOT have your cell phone on during cl or be taking or making calls. That's very rude and should be saved for later. Sounds like your professors have had a lot of problems with kids interrupting cl and had to make up a rule about it to stop it.