"It will be more like Prohibition-era America, but with hidden rifles substituting for stockpiled hooch..."

What Will Gun Controllers Do When Americans Ignore an ‘Assault Weapons’ Ban? - Reason.com: "Prohibition was kneecapped by Americans' widespread refusal to stop producing, selling, and drinking booze. Millions of Americans smoked marijuana decades before majority sentiment creeped toward legalizing the stuff. Gays and lesbians not only surreptitiously lived and loved when they were targeted by the law—they also famously (and righteously) stomped cops who raided the Stonewall Inn, ultimately precipitating liberalization. And restrictions on exporting encryption were eased only after cryptographers illegally exported code—even printing it on T-shirts as an act of civil disobedience...

"The term assault weapon itself, of disputed origin, is a thorn in the side of gun enthusiasts, who point out that the differences between 'assault weapons' and other semi-automatics are largely cosmetic and don't increase the gun's lethality," explains Slate senior editor Rachael Larimore, in a piece taking the media to task for reporting and editorializing on guns without getting the facts straight. "Because these guns are really just ordinary rifles, it is hard for legislators to effectively regulate them without banning half the handguns in the country (those that are semiautomatic and/or have detachable magazines) and many hunting rifles as well," adds UCLA law professor and gun control advocate Adam Winkler, who has actually done his research...

In 1990, even before opposition had become so hardened, California experienced similar resistance to its original restrictions on "assault weapons." "As a one-year registration period draws toward an end on Dec. 31, only about 7,000 weapons of an estimated 300,000 in private hands in the state have been registered," The New York Times reported. When New Jersey went a step further and banned the sale and possession of "assault weapons," 947 people registered their rifles as sporting guns for target shooting, 888 rendered them inoperable, and four surrendered them to the police. That's out of an estimated 100,000 to 300,000 firearms affected by the law. The New York Times concluded, a bit drily, "More than a year after New Jersey imposed the toughest assault-weapons law in the country, the law is proving difficult if not impossible to enforce." 

But let's go with it. So, the government somehow defines "assault weapons" in a meaningful way and bans sales of new ones. How is that going to be effective given the millions of disfavored weapons already in circulation? That includes roughly 8 million AR-15-style rifles alone—out of somewhere north of 300 million firearms in general. It's not like they're going anywhere...

And their numbers will increase, even if commercial production and sales are outlawed. People have been 3D-printing AR-15 lower receivers (the parts legally classified as a firearm) for years. More durable receivers are CNC-milled by hobbyists from partially finished blanks as well as raw blocks of metal. These techniques were developed in anticipation of the laws now proposed, with the specific purpose of rendering them impotent. Molon labe, remember? 

So, a United States the morning after, or a year after, or a decade after a successful effort to ban "assault weapons" will not be the scene of the "domestic disarmament" favored by prominent communitarian sociology professor Amitai Etzioni. It will be more like Prohibition-era America, but with hidden rifles substituting for stockpiled hooch and 3D printers standing in for moonshiners' stills. And probably a bit more tense. Those defiant gun owners will also be included in the jury pools chosen to sit in judgement of unlucky violators scooped up by law enforcement. That situation will likely replicate the difficulty prosecutors had in getting convictions of Prohibition scofflaws in the 1920s and marijuana law resisters today...""