I'll feel a lot more comfortable with the whole Second Amendment Sanctuary thing when people can buy and sell guns freely and publicly without fear of repercussions in counties like Nye. Like people posting online "no background check" and doing the sales/transfers without repercussions in X rural county.
Sure, the sheriff may not care to investigate, but the DA also has the ability to press charges (and so does the Attorney General). Though, if I recall correctly, in Nevada the prosecution must be in the county where the offense occurred, so the county judge might just throw out the case entirely as unconstitutional. In the 1960s, this happened with open carry in Reno. A judge disagreed with the ordinance, deemed it unconstitutional and threw out a case, and it caused fits across the biggest little city.
Juries are the best bet. Of course, any seller charged with not getting a background check on the buyer will probably be some dirtbag criminal in Clark County. For instance, the first prosecution for Washington's UBC law was the guy who sold a gun to someone who committed a murder. Apparently, both people were not upstanding citizens.
Even DA Wolfson said that normal, law abiding gun owners are not who he's worried about (and probably won't devote much time against). Even so, you don't know who the next prosecutor in the big cities will be or what the political climate might be. You also don't want to flout the law, taking a chance that nothing will come of the sale, only to find out your buyer committed a mass shooting (like Douglas Haig).
Background checks breaking the law are likely to go under the radar. But I'll be a believer when violations happen openly and nothing happens, sorta like how high capacity magazines are still sold openly in much of Colorado, despite the ban. The real test will be with any assault weapon ban or something worse. When those bad things are still openly sold and no one dares or cares to enforce that law in the rural counties, then the 2A sanctuaries will be a success.
But then again, fireworks purchasers are busted regularly by NHP and Metro coming back from Pahrump. Granted most of them are speeding and have the fireworks in plain sight in their car, but cops still enforce it (half-assed, like they take half the fireworks and then wink at the rest). But it's not out of the realm of probability for hostile county LE to enforce the laws once you get back to their jurisdiction. I'd imagine that kind of enforcement would quickly result in an ambush and dead cops (though I bet a lot of Nevada cops would simply balk at the idea in the first place).
Anyhow, the rambling musing is complete. Time will tell with how the 2A sanctuaries shape up, but as the saying goes, money talks and BS walks.