While automatic weapons are supposed to be heavily regulated, for 15 years it was possible to buy them without doing the required notification of local law officials. In fact, it was possible to buy a military-grade machine gun without so much as the background check faced by ordinary gun owners.

Many local law-enforcement officials refuse to approve the transfer of machine guns, silencers and other heavily regulated weapons to residents in their jurisdictions. As a workaround, gun owners have obtained them through the use of trusts, legal entities that don’t require permission from sheriffs or police chiefs.

The wide-open period of using trusts to bypass laws around automatic weapons began in 2000, when a loophole in the law became obvious. Over the next 12 years, some 40,000 gun trusts were created to hold an unknown number of automatic weapons. Finally, in 2012, the Obama Justice Department moved to correct this problem along with another that was closely associated.

As of April, 630,019 machine guns were registered with the Bureau of Alcohol, Tobacco, Firearms and Explosives, including more than 11,700 in Nevada, up from 456,930 machine guns in 2010.

Even with the new order being issued in 2012, it took until 2016 for ATF to finalize rules for handling gun trusts. And while trustees are now subjected to the same background check as other applicants, it’s still not clear if these new rules subject those who apply under a trust to the same restrictions by local authorities that apply to individuals.