The restrictions on discharging are the same for any automotive refrigerant. It's particularly silly to have such restrictions on discharging 134a, since you can buy cans full of it which are intended to be discharged, but the restrictions are there nonetheless. The rule is, if it is a refrigerant in a car or sold with the intention to go into a car, you can't discharge it, regardless of the chemical makeup. You can thank the mobile air-conditioning society for that one.

You can take an online test for about $20 which will enable you to legally purchase R12. There is still vast quantities of the stuff for sale in this country. Sure, the price is higher than for 134a, but it's still almost the cheapest part of the entire system.