http://www.thefirearmblog.com/blog/2014/06/19/scotus-upholds-atfs-straw-purchase-prohibition/
In deciding against Petitioner Abramski, the Court held that when Abramski answered yes to Question 11.a on the 4473 (the actual buyer question), he made a false statement with respect to a fact material to the lawfulness of the disposition, which violated 18 U.S.C. § 922(a)(6). The Court also held that his misrepresentation concerned information required to be kept by the GCA, which violated 18 U.S.C. § 924(a)(1)(A).
922 a.
(6) for any person in connection with the acquisition or attempted acquisition of any firearm or ammunition from a licensed importer, licensed manufacturer, licensed dealer, or licensed collector, knowingly to make any false or fictitious oral or written statement or to furnish or exhibit any false, fictitious, or misrepresented identification, intended or likely to deceive such importer, manufacturer, dealer, or collector with respect to any fact material to the lawfulness of the sale or other disposition of such firearm or ammunition under the provisions of this chapter;
The muzzie shooter farookie would have cleared a background check-and his state department vetted wife too I reckon. I guess it depends on kaliforny law if private firearms sale is legal between individuals. And if not depends on when farookie bought the rifles- could have been legal at that time. Fact is it is very illegal everywhere to murder a bunch of people.