The Syrian government massacred at least 108 civilians in the village of Houla this past weekend, so the US responded yesterday by ordering the expulsion of Syria’s top diplomat in Washington.

That’s what passes for tough justice in DC these days: No more power lunches for Syria’s chargé d’affaires, who has to return to Damascus.

That’ll show ’em, right?

Wrong.

If Syria’s civilians look like an endangered species these days, it’s because they are: As many as 12,000 have been killed over the last 15 months — and there’s no sign that the slaughter will slow.

Several other Western powers also expelled Syrian diplomats in the hours before the US announcement, but stopping the killing will take more than symbolic gestures from the “world community.”

It’ll take real American leadership — and here things become truly confounding.

First of all, as noted, Washington’s expulsion was preceded by similar action by many other nations: America, as is the case these days, followed — it did not lead.

President Obama said the animating principle behind his military intervention in Libya last year was to protect America’s “interests and values” — which meant preventing a “massacre that would have reverberated across the region and stained the conscience of the world.”

But it’s hard to square one with the other: Massacres in Libya are unacceptable, but in Syria they’re just part of daily life?

It’s easy enough to see why: Obama the politician isn’t interested in opening new hostilities before the November elections.

But in sitting still he’s squandering more than Syrian lives — he’s also squandering America’s role as a global leader and Middle East power.

America does in fact have interests and responsibilities in Syria, which is Iran’s sole Arab ally and its port on the Mediterranean. Cutting out Bashar al-Assad and cutting off Iran are very much to be desired. Letting Assad prosper sets the region back.

But the White House is still hiding behind the UN as a cover for inaction. The State Department expressed its disgust with Syria for violating its “UN Security Council obligations” — making the case against massacres in the namby-pamby language of international law.

When the UN leads the way, no one does. When everyone is in charge, no one is.

It’s not clear what the next step should be. Sen. Lindsey Graham (R- SC) yesterday called for a no-fly zone over Syria. Other lawmakers have called on Obama to provide direct military aid to the rebels.

But sitting idly by aids neither US interests nor Syria’s endangered civilians.

Expelling second-rate diplomats doesn’t cut it, either. (Copyright 2012 NYP Holdings, Inc. 05/30/12)