As of Tuesday, adults younger than 21 are no longer allowed to buy semi-automatic rifles in Washington, thanks to a ballot initiative approved by 59 percent of that state's voters last November. The initiative, I-1639, officially targets "semiautomatic assault rifles," but its definition of that term is so broad that it renders the assault part superfluous, except for tendentious rhetorical purposes.

The New York Times, for example, describes the firearms restricted by I-639 as "assault weapons" (a term the initiative also uses) and implies that they are similar to the guns banned under that heading in "states like California and Connecticut." While those laws do cover semi-automatic rifles, they do not cover all semi-automatic rifles—only specifically named models or those with disfavored features such as pistol grips, folding stocks, and flash suppressors.

I-1639, by contrast, defines a "semiautomatic assault rifle" as "any rifle which utilizes a portion of the energy of a firing cartridge to extract the fired cartridge case and chamber the next round, and which requires a separate pull of the trigger to fire each cartridge." That category includes not just scary-looking, military-style rifles like the AR-15 but a wide range of firearms commonly used for hunting, target shooting, and competitions. The definition excludes rifles that are "manually operated by bolt, pump, lever, or slide action" but includes all the rest.

In addition to the new minimum purchase age, the initiative imposes a 10-day waiting period on buyers of semi-automatic rifles and bans sales to residents of other states; those provisions take effect in July. According to the initiative, the restrictions are supposed to help prevent mass shootings.

Since the Times does not even hint at the broad scope of I-1639, readers may be puzzled by objections to the law. "We will not sit idly by while elitist anti-gun activists attempt to deny everyday Americans their fundamental right to self-defense," says Chris Cox, executive director of the National Rifle Association's Institute for Legislative Action, in a statement quoted by the Times. But if 18-to-20-year-olds are denied the right to purchase "semiautomatic assault rifles," can't they still purchase ordinary semi-automatic rifles?

Well, no, they can't, but readers won't understand that point unless they are familiar with I-1639's sweeping definition of "semiautomatic assault rifle." Since the minimum purchase age for handguns in Washington was already 21, the only remaining options for younger adults are shotguns or "bolt, pump, lever, or slide action" rifles. That situation makes the NRA's concern about the "fundamental right to self-defense" easier to understand. The NRA is one of the plaintiffs in a post-election lawsuit that claims I-1639's age restriction on rifle purchases "impermissibly burdens the exercise of rights guaranteed by the Second Amendment" and is "significantly broader than necessary to serve any possible alleged governmental interest."

The response from the initiative's supporters is telling. "The gun lobby is trying to thwart the will of nearly 60 percent of Washingtonian voters who supported common-sense gun reform in our state," Washington Attorney General Bob Ferguson told the Times. But the Second Amendment is supposed to thwart the will of the majority; that is the whole point of constitutional guarantees. The NRA may or may not be right that I-1639 violates the Second Amendment. But the fact that most Washington voters thought the initiative was a good idea has no bearing on that issue.

Linda Greenhouse, who covered the Supreme Court for the Times from 1978 until 2008, also does not like the idea that the Constitution might trump her policy preferences. In an op-ed piece published today, she pooh-poohs the "outlandish" notion that federal courts are treating the Second Amendment as a "second-class right," saying that concern is a right-wing fantasy dreamed up by Justice Clarence Thomas and echoed by likeminded extremists. Then Greenhouse proves Thomas' point by complaining that "the Supreme Court's appetite for expanding the Second Amendment, if such an appetite develops, will be wildly out of sync with the mood of the country." If the Court overturns popular policies just because they violate the Constitution, she says, it will "accelerate the collapse of public confidence in the one organ of government that at the moment seems to stand between us and disaster."

The Court's ability to "stand between us and disaster," of course, depends on its determination to uphold the Constitution regardless of politics or public opinion. Yet Greenhouse wants the justices to consider the latest polling data before deciding how to apply the Second Amendment. It seems unlikely that she would take that position in connection with any other constitutional right.