Senator Claire McCaskill (D-Mo.) said Tuesday she's in favor of making young women register for the draft — and two top-level military officers agreed.

The topic came up during a hearing of the Senate Armed Services Committee and represents the first time high-level military leaders have commented in recent years about women joining the draft.

Leaders of the Navy, Marine Corps, and Army were called to testify about opening all combat jobs to women. The Secretary of Defense announced in December 2015 that he was dropping all remaining exclusions to women serving in direct-combat career fields like the infantry, armor, and special operations forces.

Secretary of the Navy Ray Mabus, Commandant of the Marine Corps General Robert Neller, Acting Secretary of the Army Patrick Murphy, and Army Chief of Staff Mark Milley all said that they support the move towards opening combat jobs.

What's less decided is how the change will impact the Selective Service.

While all male U.S. citizens and residents between the ages of 18-26 are required to register, women have been exempt from draft registration--specifically because they were excluded from combat jobs.

A 1981 U.S. Supreme Court case is the basis of that rationale. In the decision, Justice William Rehnquist wrote that since the purpose of a draft is to fill combat jobs, and women are expressly prohibited from those jobs, then it is Constitutionally permissible to have only men register for the draft.

"I think of the things we have to address now is registering for the Selective Service," McCaskill said Tuesday. "The rationale used for saying there was no requirement for women to register for the Selective Service has now been eliminated."

She went on to note she supports having women register, and feels that registration may increase the number of women volunteering for military service.

Generals Neller and Milley said they'd support such a change, while Mabus and Murphy said only that the issue of changing the law should be studied.

Congress could change the Military Selective Service Act--or the male-only provision could be ruled unconstitutional by the courts.

There is such a lawsuit underway in California.

Plaintiffs attorneys in the National Coalition For Men v. the Selective Service System are waiting to hear if a three-judge panel on the 9th Circuit of Appeals will order a court date to hear their case.