Survivors of the massacre at a Parkland, Fla., high school have held vigils, angrily chanting “No more guns!” They’ve demanded that state legislators outlaw the AR-15, the kind of rapid-fire weapon with which 17 of their classmates and staff members were killed.

Other students added their voices to the anti-gun-violence chorus. In Washington, D.C., they marched on the U.S. Capitol, shouting: “Our blood, your hands!”

Similar expressions of pain and frustration, outrage and determination, have followed previous school shootings. But up until now, they have been drowned out by three little words: the Second Amendment.

Their Latin equivalent is “veto.” By proclaiming that word, an ancient Roman official called the Tribune could halt debate in the Senate if he felt Rome’s legislature was headed in an unacceptable direction.

Now it’s pretty much the same with us. Invoking the Second Amendment effectively ends even modest proposals for gun control.

The knock-out power rests on the assumption that Americans’ right to keep a gun for their personal safety is embedded in the Second Amendment. Yet if that is so, the Founding Fathers must have dug a really deep hole to house that entitlement.

Because for 220 years, no one uncovered it.

The Second Amendment went into effect with the ratification of the U.S. Constitution in 1788. It only gained a stranglehold over gun-control efforts in 2008. That year, by a 5 to 4 vote, the U.S. Supreme Court struck down Washington, D.C.’s gun regulations.

The court’s majority ruled that Washington’s law infringed on residents’ right of self-defense — a right guaranteed by the Second Amendment, according to the justices.

That decision required a bit of legal gymnastics, since the term “self-defense” doesn’t appear in the Second Amendment. Its writers tied gun ownership to “a well regulated militia being necessary to the security of a free state.”

In fact, the Supreme Court used that militia phrasing to support gun-control laws, long before it decided that the words meant that Washington’s gun-control law had to go.

In the 1930s, a well-known bank robber claimed his Second Amendment rights had been violated by a federal regulation requiring that sawed-off shotguns be registered. The law had been enacted in response to Prohibition-era gang wars.

The Supreme Court rejected the fellow’s argument, saying it couldn’t see how a “shotgun having a barrel less than 18 inches long has today any reasonable relation to the preservation or efficiency of a well regulated militia.”

The court’s flip-flop on gun control in 2008 wasn’t unique. Such reversals are usually explained as in line with an evolving body of jurisprudence, or some such explanation. But that leaves me with a vexing question about the judiciary:

You mean it took them 220 years to figure out that the Founding Fathers meant to say what they didn’t say?

I’m more comfortable with what the great humorist Will Rogers once observed: “The Supreme Court reads the election returns.” Crime rates soared in the run-up to the

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