Today, there is one major way in which federal law in America explicitly discriminates between women and men.

All men 18 to 25 must register for military service or lose access to a variety of government benefits, including student aid; women are exempt from the registration.

That would change under legislation introduced last week by Rep. Duncan Hunter (R-Calif.) and Rep. Ryan Zinke (R.-Mont.).

Their legislation would extend Selective Service to women. The bill might not be intended seriously. Duncan, at least, strongly opposes new policies opening all combat roles to women and is apparently trying to force debate on the issue.

But in fact, ending sex discrimination in this area — whether by including women in draft registration or by abolishing it — should be a no-brainer.

Objections to women in combat have been based on several rationales. One is practical: Critics argue that gender differences in physical abilities make women less efficient in ground fighting and that mixed-gender troops are likely to have worse cohesion. These issues need to be examined honestly, without regard to either traditional prejudices or newfangled “political correctness.”

Among other things, a recent study which concluded that gender-integrated Marine units performed worse than all-male ones, and which Hunter and others claim was rejected by the brass for political reasons, should be impartially reassessed. Special training to improve women’s performance is worth looking into. So is the controversial option of all-female units, which have done well in other nations — in Kurdistan, for example.

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What shouldn’t hold back change is the argument based on chivalry.

Sen. Ted Cruz (R-Texas), the Republican presidential candidate, has said that it’s “immoral” to “draft our daughters to forcibly bring them into the military” and “put them in a foxhole with a 220-pound psychopath trying to kill them.”

But why shouldn’t we be as horrified by the prospect of forcibly putting our sons (or brothers and husbands) in close combat? Whether the message is that young men are more expendable or that young women should be more sheltered, it’s ultimately unfair to both.

Draft registration is a separate issue. Conscription did not exist in the United States before the Civil War and was often seen as incompatible with liberty. At present, we have not had a draft in more than four decades; registration is viewed as a slightly bothersome formality that does not cause young men to feel aggrieved, but also does not inspire much patriotism.

Writing in The Washington Post, former U.S. Navy officer Christopher Preble, vice president for defense studies at the Cato Institute, argues that Selective Service is an anachronism that should be ended. (Disclosure: I am an unpaid media fellow with Cato, a libertarian research center.) Preble says our modern wars do not require mass conscription and that, if an emergency required a draft, it could be easily conducted without advance registration.

As a policy matter, Preble is almost certainly right.

But if only for symbolic value, I would favor at least a five-year period of draft registration for both sexes. It would send a powerful message that, if an actual draft were needed, it would include both men and women, and they could serve wherever their contributions would be most effective. Equal rights must come with equal responsibilities.

So two cheers for the Hunter-Zinke bill. Even if it was meant to subvert the equalization of military roles, there’s nothing to say it can’t have the opposite effect. The ban on sex discrimination was originally inserted into the 1964 Civil Rights Act by opponents of the law who sought to undermine it. Progress can happen in mysterious ways.

Cathy Young is a regular contributor to Reason magazine and Real Clear Politics.