President Obama’s about-face on seeking congressional authorization to strike Syria was ultimately a political decision. On the one hand, he claims it is not legally necessary, and yet he knows he’s politically vulnerable. Thus he punted to Congress, demanding authorization to bolster support.

But where does this leave us legally? Does the War Powers Act require congressional authorization or not? Republicans who used to hate the War Powers Act’s restrictions on presidential war-making powers now argue that authorization is legally required. And Democrats who once clamored for authorizations in the Afghan and Iraq wars now assert Mr. Obama’s right to bypass Congress.

What’s going on here? Some history may clarify.

The War Powers Act of 1973 was largely a Democratic project, promoted in the wake of the Vietnam War. At the time, Republicans opposed requiring strict congressional approval of wars, arguing that it was unconstitutional and interfered with the constitutional prerogatives of the commander-in-chief. The act imposed a 90-day deadline on military operations launched by the president without congressional authorization. It passed over President Nixon’s veto.

The Democrats’ eagerness to seek congressional approval of military operations ended during the Clinton presidency. Faced with acts of genocide in the Balkans, Mr. Clinton gained neither congressional nor U.N. Security Council authorization for the military campaign against the Serb-dominated remnant of Yugoslavia over Kosovo. The operation was conducted under the aegis of NATO and ended 12 days before the 90-day deadline set by the War Powers Act. Technically, the act had not been violated. But it was abundantly clear that, with a Democrat in the Oval Office, Democrats had a different attitude about the need for congressional approval of military operations.

So, too, did Republicans. They were divided over the Balkan intervention, and some felt that Mr. Clinton was bypassing Congress. The shoe was on the other foot, and a lot of Republicans didn’t like it.

Fast forward to the Iraq War. Now the Democrats were out of power, and many who opposed the war fell back on the pre-Clinton-era standard of strict congressional approval for wars. Hence the demands for both congressional and U.N. authorizations before storming into Iraq. It was like a replay of the ‘70s, with congressional Democrats trying to restrain a supposedly warmongering Republican president.

The Republicans did a switch too. The military campaigns in Afghanistan and Iraq would clearly extend beyond the deadlines of the War Powers Act, so when President George W. Bush sought congressional authorizations for them, the question of compliance with the act was moot. Still, the principle of seeking congressional authorization had been established by a Republican president, and that was new. It raised a standard with which Mr. Obama now lives.

In Libya, however, he ignored it, bypassing Congress altogether. Instead, he argued that it was an indirect military operation in support of NATO. Authorization by the United Nations Security Council was sufficient.

With Syria it’s a different story. Mr. Obama will seek congressional authorization, even though he could argue his proposed “limited” response would be consistent with the War Powers Act (if the operation lasts less than 90 days). Still it is clear that he would have preferred to bypass Congress in this instance, just as he had done with Libya. And, if Congress votes against him, he may strike Syria after all.

As for the Republicans, they are all over the place. Some demand authorization, and some do not. Some call for an official declaration of war. Whatever may be said about them today, many (possibly most) have abandoned their old position of championing the constitutional prerogatives of the commander-in-chief to make war.

If all this makes your head spin, join the club. We don’t need a new law, but we could be more consistent when it comes to seeking congressional authorization of military action. Right now it seems mostly to be about which political party occupies the White House.

- Kim R. Holmes, a former assistant secretary of state, is a Distinguished Fellow at The Heritage Foundation.