The United States faces no serious military threats today, yet is constantly at war. Syria is the latest target.

Traditionally Washington did not look for wars to fight. The government’s duty was to protect the American people from conflict.

Measured on this scale there is no cause for intervening in the Syrian imbroglio. The regime has little capacity to harm the U.S. or resist the overwhelming retaliation that would occur in response to any attack. Syria’s chemical weapons have little more utility than high explosives and nothing close to the killing capacity of America’s many nuclear weapons.

The possibility of radical Islamist insurgents gaining control over territory is more worrisome, but is most likely in the event of U.S. intervention against the Assad government. The conflict is destabilizing, but friendly states should deal with the consequences.

Of course, the Syrian civil war is a tragedy, like many others throughout history. Civil wars may be the worst, often with few genuine good guys.

The rebels are united only by their opposition to Assad. The strongest factions appear least interested in a liberal, democratic future for Syria and most interested in using Syria to attack Americans.

Nor is the contest likely to end after the first extended round. If Assad survives, he still may never reestablish his control over the entire country. If the rebels win, they are likely to engage in a new round of fighting for dominance. Moreover, there is likely to be even more score-settling with those who backed the regime.

The last argument for intervening in Syria is the regime’s apparent use of chemical weapons. Apparent because while Damascus has no moral compunctions about killing, it has no obvious reason to use such small quantities of chemical agents—enough to spark international intervention, but too little to achieve any useful military purpose. In contrast, insurgents have an incentive to use captured supplies in an attempt to draw in the West.

Assume, however, that the Assad regime used chemical weapons. The best U.S. response would be no response. First, President Barack Obama has no legal authority to strike Syria, absent an imminent threat, without congressional approval.

Second, the use of chemical weapons does not justify war. Syria is not a party to the claimed “international consensus” against chemical weapons, having never joined the Chemical Weapons Convention. Although classed as a weapon of mass destruction, chemical agents are difficult to deploy and not uniquely deadly. At least 99 percent of the battlefield deaths in World War I were caused by other means.

The last argument for war is credibility. If the president doesn’t back up his threat, who will take him seriously in the future? It’s a fair contention, except that American presidents routinely make threats on which they don’t make good. To take military action on behalf of peripheral interests would be irresponsible even if doing so marginally enhanced U.S. credibility. Washington should erase the chemical “red line” and in the future put U.S. credibility on the line only when substantial U.S. interests are at stake.

As I point out in my latest article on National Interest online:

“The case for nonintervention remains compelling. It is not in America’s interest to get involved in a conflict that looks to be a toxic mix of Lebanon, Somalia, Iraq, and Libya at their worst. Washington will make far more enemies than friends, and will find it hard to exit, no matter how gingerly it enters.”

The American people oppose intervention. Nor is it in the president’s political interest to drag the country into war. George W. Bush’s presidency will forever be defined by the Iraq War, which sucked the life out of his domestic policy agenda. So, too, it will be for President Obama if he embarks upon another unnecessary war against a Muslim country in the Middle East.

The administration should draw only one red line: against involvement in the Syrian civil war.