Laws aren't the solution you're looking for to crimes like the massacre in Las Vegas.
J.D. Tuccille writes:
Stephen Paddock "appears to have used at least one fully automatic rifle" during his murderous rampage in Las Vegas, according to the Wall Street Journal. Let's tentatively accept that for the moment while recognizing, as Nick Gillespie has noted, that early reports in situations like this are often wrong. If true, though, it demonstrates the pointlessness of the predictable calls for tighter gun restrictions issued by the usual suspects. That's because automatic rifles—machine guns—have been tightly regulated at the federal level since 1934, and subjected to further restrictions since then.
The history of federal machine gun regulations is well-covered at the website of the Bureau of Alcohol, Tobacco, Firearms, and Explosives. Regulation began with the National Firearms Act of 1934, which imposed a $200 tax on the manufacture and transfer of "shotguns and rifles having barrels less than 18 inches in length, certain firearms described as 'any other weapons,' machineguns, and firearm mufflers and silencers" at the federal level (states and localities have always been free to impose their own restrictions). According to the ATF, "As the legislative history of the law discloses, its underlying purpose was to curtail, if not prohibit, transactions in NFA firearms."