In most cases if a state declares a substance or procedure to be illegal it doesn’t prohibit one from going to another state where said substance (marijuana) or procedure (abortion) is legal.
But this isn’t the case with firearms. How can a state (NY for example) prohibit a resident of that state from purchasing a firearm in another state?
I understand, and respect the fact, that a state can prevent the resident from bringing the newly purchased firearm into the state.
I understand that the state can prevent non-residents from bringing a firearm with them even though it's legal in the other state. But on what grounds can a state prevent a purchase in another state. One can have a second home there; one can have family; one may be able to store the firearms there.
Is this situation unique to firearms or do such prohibitions exist in other arenas as well?