Come to think about it. They are allowed to sell sex (LE/police sting using BP ads) but it it is illegal for you to buy sex (so you can get caught and arrested). The law is entrapment. Is it not? Is this not unconstitutional?
There is definitely a decent case for this argument. The government provides immunity to sellers of a supposedly illegal transaction which causes the buyers to engage in an illegal transaction. It could be said that if the sellers weren't immune, they wouldn't be selling, and therefore the buyer wouldn't be buying. The government would thereby be indirectly encouraging sellers (by providing immunity) to cause buyers to commit an illegal offense which otherwise may not have occurred without government sponsorship.

