2004 Toyota Sienna Airconditioning in van

Hi, I have a Toyota van 2004. Recently, the ac began blowing warm air, not hot, through the vent on the driver's side. The passenger side vent still blew cool (ac) air. I took it to the mechanic to have it just diagnosed. When I got it back I was told that there's a leak that would need to be fixed. I paid the labour fee and left wanting to think it over whether to have it fixed right away or wait. I decided to wait but to my dismay, I found now I don't have any ac at all. I took it back to the garage and told them so. Then they surprised me with the information that that they drained the refrigerant entirely because there was a leak. They didn't say how big the leak was. They also told me that there's a law that doesn't allow a mechanic to let the vehicle go without draining the refrigerant if there's a leak. We have no means to fix the leak right now and we now have no ac as well. Just tell me please, is this true that there's such a law in Ontario, Canada? I need to know because I can't help but feel that it's a misinformation.