Straw purchasing isn’t an issue in most countries. Buying a weapon may include background checks, psychological evaluation, safety training, being a member at a range or club for 6+ months or even military service. It doesn’t end there either, with many countries requiring registration of purchased firearms with heavy fines if you’re unable to produce the weapon when asked.
Luckily for cartels and criminals, Americas gun laws are dogshit. With private sales, you don’t even need to pass a background check in some places. Straw purchasing isn’t just viable, it’s the fastest, easiest, lowest risk way to secure practically any semi-automatic weapon you want.
But no matter how serious or widespread those failures are, the pro-gun community staunchly opposes addressing them, backed by lobby groups who are keenly aware their profits would be quartered if gun regulations worked.