We don’t have to look to New Zealand’s recent flop of a mandatory buyback, where less than 10 percent of the country’s estimated number of newly banned weapons have been handed over so far, to answer those questions. There’s a great case study right here in the bluest of blue states: New York.

Gov. Andrew Cuomo hailed the 2013 New York SAFE Act as the toughest gun control law in the nation, and one of its most important provisions was the mandatory registration of all “assault weapons” in the state. This isn’t a confiscation or even a ban, so it’s nowhere near as severe as what O’Rourke and others are pushing—it’s just a teeny weeny little registration requirement.

So how has that worked out? Well, according to the National Shooting Sports Foundation’s conservative estimate, New Yorkers owned about 1 million “assault weapons” at the time the ban was passed. So the 44,000 that were actually registered are about 4 percent of the total. This noncompliance with the law is widespread and mostly open, but the police aren’t doing much about it.