“HELL YES, we’re going to take your AR-15, your AK-47. We’re not going to allow it to be used against our fellow Americans anymore.” Democratic presidential candidate Beto O’Rourke got a lot of applause for that comment from the audience at the recent Democratic debate, but he has come under sharp criticism — including from Democrats who favor gun control — for advocating not just a ban on assault weapons but also a mandatory buyback. Mr. O’Rourke is clearly pushing the envelope, but that doesn’t mean the proposal shouldn’t be debated. Politics aside, there is considerable logic to his position.

If you believe, as do we and a majority of Americans, that weapons designed for war should be banned because of the clear and present danger they pose, it makes little sense to ignore the estimated 16 million assault rifles in circulation. That’s why after their countries were shaken by ghastly mass shootings, Australia and New Zealand instituted mandatory gun buybacks. And it’s why when the ban on bump stocks — devices that allow semiautomatic guns to mimic machine gun fire — went into effect, the Trump administration ordered owners to turn their devices in to be destroyed.

A mandatory gun buyback would face legal and logistical obstacles. Could it be conducted safely and effectively? At what cost? Why not start with a voluntary recall? How about allowing people to keep the guns at shooting clubs for recreational use? David Chipman, a retired agent with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives and now an adviser to the Giffords Law Center to Prevent Gun Violence, has suggested an approach similar to that taken when automatic weapons were outlawed in 1986, requiring the firearms to be registered and heavily regulated but not confiscated. “In some regards, this horse is out of the barn. For years, we’ve allowed these to be sold,” Mr. Chipman told the Christian Science Monitor. There were an estimated 1.5 million assault weapons in 1994 when a federal ban went into effect. When Congress allowed the ban to expire a decade later, sales soared.

Of course, there is no “politics aside” when it comes to guns. President Trump and Republican leaders in the Senate said Mr. O’Rourke’s comments have set back efforts to reach bipartisan agreement on more modest measures such as universal background checks and red-flag laws. Then again, Mr. Trump has found so many excuses for inaction and flip-flops on guns that it’s hard to keep track.

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