Panetta was right that the Pentagon doesn’t have the authority to mandate that women ages 18 through 25 register for Selective Service, as their male counterparts must do today. Only Congress can change that law. But the Pentagon is not totally off the hook.

Whenever the defense secretary opens new combat positions to women, he’s required by law to provide Congress with a detailed analysis of the legal implications for the constitutionality of the Military Selective Service Act.

Senior defense officials acknowledged last week that providing Congress with that report would be the next step the Pentagon would take but did not have any other details.

Although the Selective Service law is inherently discriminatory — requiring something of men that it doesn’t require of women — it was considered constitutional because women were excluded from combat. Since women wouldn’t be conscripted, they didn’t need to register. Now that women will be joining at least some combat units, Congress eventually must determine how to handle that new reality.