Isn't it illegal to add Freon without repairing the leak first?
No sorry it is not I believe its systems that are 50 lbs and more the leak has to be fixed
found it:
The leak repair requirements, promulgated under Section 608 of the Clean Air Act, require that when an owner or operator of an appliance that normally contains a refrigerant charge of more than 50 pounds discovers that refrigerant is leaking at a rate that would exceed the applicable trigger rate during a 12-month period, the owner or operator must take corrective action.