Let's deal with a hypothetical to actually examine how we think about Supreme Court decisions, processes, and logic.
So, Kennesaw Georgia has had a law on the books since 1983 that requires the head of every household to have a gun.
To my knowledge this law has never received significant challenge in the courts because Kennesaw is a small town and the law has never been enforced.
Now, imagine if the law were to be enforced.
Say the state didn't come into your house and force you to show law enforcement that you have a gun and that you're in compliance with the law; but, they enforce it through local taxes. If you show a receipt that you purchased a gun, that's a tax write-off. A gun that you have in your possession would be declared as a small property tax. If you declare no gun ownership in your tax forms, you are penalized a few hundred dollars and the government issues you a gun.
I'm sure my many friends who are not as pro-2A as I am would hate this law and demand that the courts strike it down. It would be a law that penalizes people for not buying something. It would be forcing people who don't like guns to operate against their values and actually give their money to an industry that they don't like.
You'd be right. That would be an awful, unconstitutional law.
The thing is, the ACA was basically passed with the same mental gymnastics that would apply to this hypothetical case. Justice Roberts threw the Obama administration a bone by saying that the fine for not buying heath insurance under the act could be viewed as a tax. If you support the Court's ruling on the ACA, it seems that you would have to support a law that raises taxes on people who don't buy guns.