Or rather, the briefs filed for the defendants (Becerra) presented convenient arguments to the judge, who was very likely pre-disposed to find for the government regardless, that there is no legally relevant difference between automatic and semi-automatic operations. Using the logic in this case, there would appear to be no barrier to banning all semi-automatic firearms, period, whether "in common use" or not.
As is often said, judges make their decision and then write a ruling to fit the decision. With every case, the anti-gun side is fine-tuning their logic to make that easier for pre-disposed judges.
Further, the Attorney General points to a United States Army manual instructing soldiers on the use of the M-16. The manual notes that, although the M-16 is capable of automatic fire, “[t]he most important firing technique during fast-moving, modern combat is rapid semiautomatic fire.” (Ex. 19 to Chang Decl. at 3, Doc. 76-19 (emphasis added).) This is because automatic fire “is inherently less accurate than semiautomatic fire.” (Id. at 7.) Thus, the military is trained to use M-16s as if they were semiautomatic rifles because the semiautomatic mode is more effective. Reviewing similar evidence, Kolbe concluded that “in many situations, the semiautomatic fire of an AR-15 is more accurate and lethal than the automatic fire of an M16.” Kolbe, 849 F.3d at 136.
Moreover, even if the ability to fire in automatic mode were significant, Congress found that “it is a relatively simple task to convert a semiautomatic weapon to automatic fire.” (H.R. Rpt. No. 103-489 at 18, Ex. 27 to Chang Decl., Doc. 76-27.) The Attorney General’s evidence shows that a semiautomatic weapon can easily be converted to automatic fire by installing certain parts, such as bump stocks or multiburst trigger activators. (Plaintiffs’ Response to AG’s SUF ¶ 13.) The Supreme Court in Staples v. United States, 511 U.S. 600 (1994) is in accord with the Attorney General’s evidence, as it noted that “[m]any M-16 parts are interchangeable with those in the AR-15 and can be used to convert the AR-15 into an automatic weapon.” Id. at 603.7
The logic used is that lethality and effectiveness, not arcane mechanics of automatic vs semi-automatic, is what matters when comparing it to a firearm that "may" be banned, "like" an M-16. A firearm that is found to be too lethal or effective by this logic can be banned, without even addressing how that impacts the core right, since it is then "like" an M-16 and has no protection whatsoever.
The only solution to this will be the Supreme Court intervening, at least in the 9th and most other circuits.