On Tuesday, the Senate passed a defense authorization bill that would require young women to register for the draft — the latest development in a long-running debate over whether women should sign up for the Selective Service. The provision would apply to women turning 18 in 2018 or later and would impose the same requirements and rules that currently apply to men.

The policy is still far from being law. The House, after considering a similar provision earlier this spring, ultimately passed an authorization bill that omitted it; the two branches of Congress now must resolve the differences between their bills. And the bill faces a veto threat from President Obama over other elements of the legislation, such as the prohibition on closing down the Guantanamo Bay military prison.

But the bill's passage brings women a step closer to Selective Service registration — a historic change that has bipartisan support in Congress but is firmly opposed by some conservative lawmakers.

For decades, the U.S. policy of having a draft for men, and not women, was approved as constitutional by the Supreme Court.

But as NPR's David Welna reported last year, the court's reasoning relied on the fact that women were barred from combat roles.

Now that women are eligible for combat duty, "Congress seems to have lost its court-endorsed rationale for limiting Selective Service registration to males only," David wrote.

Influential lawmakers are on board for registering women — Sen. John McCain, the chairman of the Senate Armed Services Committee, is one of them.

And as The Two-Way noted earlier this year, top leaders from the Army and Marines have testified before Congress that they, too, think women should register.

Currently, men 18-25 must register for the Selective Service. "It's worth noting that while people are still required to register, the draft was ended in 1973 and the military became an all-volunteer force," The Two-Way has reported.

Some conservative lawmakers remain fiercely opposed to women's registering for the draft, The New York Times reports, noting that Sen. Ted Cruz said on the Senate floor, "The idea that we should forcibly conscript young girls in combat to my mind makes little sense at all."

The defense authorization bill passed the Senate decisively on Tuesday, The Associated Press reports, with a final vote of 85 to 13.

The section dedicated to women and the draft was a small section of a lengthy bill authorizing $602 billion in defense spending.

President Obama has threatened a veto over several elements of the bill, which would block his administration from closing the prison at Guantanamo Bay, deny the Pentagon its request to shut down surplus bases and limit the size of the president's National Security Council, the AP reports.

Meanwhile, many senators are angered by provisions missingfrom the bill — amendments that couldn't be considered thanks to gridlock in the Senate.

Republican Sen. Mike Lee of Utah was calling for an amendment to prevent the federal government from indefinitely detaining U.S. citizens. When the Senate wouldn't bring it to a vote, he functionally blocked votes on other amendments — including a measure of his own, calling for a debate on women and the draft.

An amendment to offer more U.S. visas to Afghan interpreters who assisted the U.S. military was among those stuck in the impasse. An angry McCain, who supported the amendment, railed against Lee on the Senate floor, Roll Call reports.

"Now we're talking about the lives of men who have put it on the line for the men and women who are serving," McCain said, referencing the threat the Taliban poses to those who aid the U.S. military. "Don't we have some sense of perspective and priority here? People are going to die."

Democratic Sen. Kirsten Gillibrand of New York was also frustrated; the impasse blocked her three-year effort to pass an amendment reforming the way the U.S. military handles sexual assault cases. She called the lack of a vote on her amendment an "abject failure on behalf of Congress."

A number of other amendments, advocated by both Democrats and Republicans, were also stymied by the dispute, The Washington Post reports.

The House and Senate will now begin work on reconciling their two different bills.

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