President Barack Obama made the correct decision Saturday in asking Congress to authorize the use of force against Syria. In doing so he is strengthening the case for military action against the Syrian regime for gassing its own people.

The president, as commander in chief, has limited authority to use force in the national interest on an emergency basis without consulting Congress. But when there is time for discussion, and the consequences of U.S. military action could be serious, it is essential for the executive to make his case to the legislative branch, as directed by the Constitution.

Some members of Congress think the president is going too far in his plans to launch air strikes against Syria. Some think he’s not going far enough. The latter group includes Republican Sens. John McCain of Arizona and Lindsey Graham of South Carolina, who were among the lawmakers meeting with the president Monday to hear his plan for air strikes in Syria.

Congress could, of course, say no, as the British Parliament did last week. That would be a serious blow to the president’s credibility, since he has repeatedly gone out on a limb by warning the Syrian regime, without consulting Congress, that the U.S. would retaliate for the use of chemical weapons.

But the evidence collected by the administration, including samples of blood and hair from victims and intercepted communications by at least one Syrian government official, makes a strong case that the Assad regime did in fact use sarin gas in an Aug. 21 attack that killed nearly 1,500 civilians, including hundreds of children.

United Nations inspectors have presumably collected similar forensic evidence that is likely to be made public in the near future.

Public revulsion against these horrors increases the likelihood that Congress will back the president. But Congress should first demand greater clarity about the purpose of the use of force — and its likely results.

If there is a flaw in the president’s approach on Syria, it concerns what he hopes to achieve.

On Saturday he said, “Our action would be designed to be limited in duration and scope. But I’m confident we can hold the Assad regime accountable for their use of chemical weapons, deter this kind of behavior, and degrade their capacity to carry it out.”

It is hard to discern a coherent strategy in that approach, beyond the desire to “hold the Assad regime accountable.”

The president has previously expressed a desire to see the Assad regime replaced. But it is not clear how a limited strike in retaliation for a violation of international law banning the use of chemical weapons advances this objective.

At the same time, the president’s legalistic reasoning seems to suggest that the United States should punish breaches of international law. That is a policy lacking practical limits and is far removed from the traditional concept that the United States should use force only when its national interests and the defense of its territory and its allies are threatened.

President Obama plans to spend the next week making his case for the military action he has in mind.

He clearly still has a lot of work to do regarding this crisis — as does Congress.