By Rob Cox
The author is a Reuters Breakingviews columnist. The opinions expressed are his own.

As the eagle flies, it's a long way from Bunkerville, Nevada to Slovyansk, Ukraine. Right now, though, the two places have something insidious in common: armed vigilantism. That parallel sadly seems to escape the many American policymakers who have accused President Barack Obama of adopting the logic of appeasement in his dealings with Russian President Vladimir Putin. They're missing a big point. If the United States can't uphold the rule of law at home, it can have no credibility abroad.

Over the weekend, South Carolina Senator Lindsey Graham joined the chorus of Republicans branding Obama the new Neville Chamberlain. He told CBS's "Face the Nation" that the president is "delusional" and his latest economic sanctions "should have been called the Russian economic recovery act" for helping bolster the Russian stock market and rouble last week.

Graham's comments echoed what I heard from an adviser to one of the world's biggest hedge fund managers last week. The "A-word," he argued, is becoming the single greatest threat to global stability. By not standing up to Putin-encouraged Russian vigilantes who are seizing towns and territory in eastern Ukraine, the United States not only gives Putin a free pass, it emboldens despots from Pyongyang to Tehran to thumb their noses at American power.

There's some truth to this. When the Kremlin's planners were considering their options in Crimea earlier this year, they certainly remembered President George W. Bush's weak response to Russia's 2008 tank joyride through Georgia. Russia decided to annex Crimea, the home of its Black Sea fleet.