During oral argument on Monday, a majority of the justices appeared likely to strike down a federal law prohibiting an “unlawful user” of marijuana from possessing a firearm — or, at least, they appeared to believe it could not be applied to Ali Danial Hemani…

It’s not just a question of marijuana; it’s also about the Second Amendment. | Jahi Chikwendiu/The Washington Post via Getty Images

During oral argument on Monday, a majority of the justices appea…