"DIY submachine guns are popping up across the West Bank," the Washington Post reported recently in a piece about a weapon that has repeatedly played a role in Palestinian attacks upon Israelis. The guns are of a common type referred to as the "Carlo," based on the Swedish Carl Gustav M/45, which dates to the World War 2 era. The article added that hundreds of the submachine guns have been confiscated over the past year, and raids staged on 35 mechanics' shops that were cranking them out.

"The Carlo has remained so popular because of how little machinery and technical know-how is required to produce it," a Times of Israel story noted earlier this year. "A drill press, some welding equipment and blueprints from the internet are all that's needed to create one of these potentially devastating weapons." The story lamented that "it's nearly impossible to prevent its production."

Ironically, Israelis themselves relied on homemade submachine guns during their War of Independence. In their case, they knocked off copies of the British-designed Sten gun and fed them with ammunition manufactured in a clandestine factory beneath a laundry. Similarly to the weapon copied by West Bank mechanics, "the Sten used simple stamped metal components and minor welding, which required minimal machining and manufacturing," according to Wikipedia.

That simplicity is a feature of many simple, sheet-metal submachine guns dating to the war era. Desperate to satisfy the need to produce massive numbers of guns in short order, designers crafted weapons that could be made in any number of existing shops using general-purpose machinery. Long before 3D printers and CNC milling machines drove headlines about DIY firearms, those characteristics made such weapons natural choices for various insurgencies battling governments in regions across the world.

Because they're so easy to produce, submachine guns also became a natural go-to for non-political manufacture in countries that have strict gun control regimes. Brazil seems to be an especially fertile source for homemade automatic weapons. There's an online cottage industry in tracking Brazilian police announcements of gun confiscations and posting photos of the creative copies of commercially produced weapons—as well as weirdly innovative original designs.

Unsurprisingly, Brazil has a thriving market for Sten guns and the like made in car repair shops because it has a severely constrained legal market for firearms. Brazilians have to jump through hoops to get government permission to purchase guns, and even if they satisfy all requirements, police can say "no" on a whim. That leaves many residents of the country without a legal means to protect themselves from the country's extremely busy criminal class (60,000 murders every year, according to some estimates). Those criminals are, of course, well-armed courtesy of that black market described above.

Some of the country's lawmakers want to make it less-daunting to legally own the means of self-defense. But for now guns remain easily available only to those willing to break the law, which leaves opportunity for DIY manufacturers.

Australia also has famously restrictive gun laws of such exquisite legislative perfection that they bear emulation, according to leading presidential contender Hillary Clinton. Well, except that the Australian government is a tad upset about gun smuggling by outlaw gangs and the hundreds of thousands of illegal firearms in circulation. Officials plan yet another amnesty for owners to surrender the illegal weapons, although Sydney University gun policy analyst Philip Alpers told ABC News that he expects it to produce only "rubbish guns" that nobody values.

Because, honestly, if you've gone through the trouble and expense of purchasing one of the "perfectly constructed MAC 10 machine guns" manufactured by a jeweler turned underground arms dealer, why would you surrender it?

Like Brazil, diversity is characteristic of Australia's illegal arms makers, who also produce submachine guns inspired by the late Philip Luty, a Briton who created designs intended for home manufacture (he was imprisoned for his troubles, but his plans are widely available). Ten percent or more of illegal guns seized by Australian police are produced by underground armorers—with powerful and easily made submachine guns featuring prominently among them.

Australia is a much safer country than Brazil, and has a lower homicide rate than the United States. But at least one academic assessment has concluded that the crime rate seems to fluctuate independently of gun ownership. That new gun amnesty is motivated not just by a black market, but by a spike in crime including murders.

Because, once again, restrictions on the legal ownership of firearms have the greatest impact on the most law-abiding segment of society who submit with little resistance. They simultaneously fuel black markets in firearms that efficiently serve insurgents and criminals (as well as principled resisters to state authority). That leaves predators with a real advantage relative to their prey.

And, if you're going to make something illegally, you might as well get the most bang for your buck out of the means you have at hand. If you're looking to supply the demand for drugs, you cook methamphetamine in motel room laboratories. And if you're supplying the illegal arms market, you download the plans for a Sten gun to a laptop in a brake-repair shop.

From the West Bank, to Brazil, to Australia, history demonstrates that if you want people to start making their own submachine guns, all you have to do is legally restrict their access to firearms of all sorts.