The ATF does not get to decide what is or is not legal. They can simply give their opinion of whether they think something is legal. So far they have given one opinion that they think PSB's are legal, and one opinion that they think PSB's are not legal. Both of their opinions have something in common. They do not change or impact the actual law.
Paraphrasing what another forum member likes to say, we each need to decide what risks we are comfortable with. But I'm not a big fan of letting the varied opinions of an administrative agency cause me to restrict my fundamental individual rights.