President Barack Obama

“The worst mistake of my presidency,” said Ronald Reagan of his decision to put Marines into the middle of Lebanon’s civil war, where 241 died in a suicide bombing of their barracks.

And if Barack Obama plunges into Syria’s civil war, it could consume his presidency, even as Iraq consumed the presidency of George W. Bush.

Why would Obama even consider this?

Because he blundered badly. Foolishly, he put his credibility on the line by warning that any Syrian use of chemical weapons would cross a “red line” and be a “game changer” with “enormous consequences.”

Not only was this ultimatum unwise, Obama had no authority to issue it. If Syria does not threaten or attack us, Obama would need congressional authorization before he could constitutionally engage in acts of war against Syria. When did he ever receive such authorization?

Moreover, there is no proof Syrian President Bashar Assad ever ordered the use of chemical weapons.

U.S. intelligence agencies maintain that small amounts of the deadly toxin sarin gas were likely used. But if it did happen, we do not know who ordered it.

Syrian officials deny that they ever used chemicals. And before we dismiss Damascus’ denials, recall that an innocent man in Tupelo, Miss., was lately charged with mailing deadly ricin to Sen. Roger Wicker and President Obama. This weekend, we learned he may have been framed.

It is well within the capacity of Assad’s enemies to use or fake the use of poison gas to suck us into fighting their war.

Even if elements of Assad’s army did use sarin, we ought not plunge in. And, fortunately, that seems to be Obama’s thinking.

Why stay out? Because it is not our war. There is no vital U.S. interest in who rules Syria. Hafez Assad and Bashar have ruled Syria for 40 years. How has that ever threatened us?

Moreover, U.S. intervention would signal to Assad that the end is near, making his use of every weapon in his arsenal, including chemical weapons, more—not less—likely.

U.S. intervention would also make us de facto allies of Assad’s principal enemies, the Muslim Brotherhood and al-Nusra Front, Syria’s al-Qaida. As The New York Times reported Sunday, “Nowhere in rebel-controlled Syria is there a secular fighting force to speak of.”

Do we really wish to expend American blood and treasure to bring about a victory of Islamists and jihadists in Syria?