I completely agree with what you're saying here. I think gun owners often dismiss the lunacy going on in other states, and look down on other gun owners who live in those states (with an attitude that "they'd move if they cared"). These gun owners often fail to realize how quickly the political landscape can change in their own state. Colorado, for instance, was a pretty red state just 15 years ago. Then we were a "swing" state. Now we're solid blue. Along with that transition has come an increasingly concerning attack on some of our civil liberties (such as gun rights).
Now, some people tell me that I should just up and move somewhere else. Well, that's easier said than done... it isn't like I haven't dreamt of the idea. This would have been easy to do 15+ years ago, but it isn't now. I have a wife and daughter in this state, and my wife's entire family is here. My career is here, and I worked hard to get to the point I'm at in my career (and wouldn't have an easy transition to just move to another state with my job). I own a house here, my friends are here, and I've simply built a life here.
The opposition has a majority in our politics, but that doesn't mean the state is entirely filled with morons... we have just enough for mob rule, but mob rule shouldn't override the constitutional rights enumerated in the founding documents of the republic in which we all live. In 2016 around 1.3 million Coloradans voted for the Democratic presidential candidate. Around 1.2 million people voted for the republican. By any measure the Democrat won by around 100,000 votes, but the "minority" party out here still represented 48% of votes cast.
What does all of this mean?
Well, to me it suggests that we can't move away from these problems. We need to start legally fighting these battles in the states in which we live. We can't just continue to give another inch, and another inch, all in the name of safety. There will never be enough gun control laws to keep the gun control lobby happy (at least not short of total disarmament).
As for the original question from this thread:
If I lived in NJ I would refuse to comply with this law. I believe such a measure to be unconstitutional, and I won't give up my rights, my freedom, or my property just because some bureaucrat tells me to do so. But, I'd probably stop keeping that property at my house, and find somewhere to cache those items for future use. I wouldn't want to get in trouble, but that doesn't mean they can have my stuff, either.