As the United States celebrates Independence Day, I can’t think of any better gift to the nation than the Supreme Court ruling last week that checked President Bush’s expanding claims of executive power.

July Fourth should remind us how blessed we are to live under rule of law. Most Americans take that blessing for granted and fail to understand how rare is the legacy bequeathed by the Founding Fathers.

A 5-3 majority on the court gave us a wake-up call.

The case, Hamdan v. Rumsfeld, was technically about whether Osama bin Laden’s former chauffeur, a Yemeni named Salim Ahmed Hamdan, who is imprisoned at Guantanamo, could be tried by military commission – a system established by Bush. The court ruled that such commissions were not authorized by federal law and violated our signature on the Geneva Conventions.

The decision also dismissed the president’s claims that his powers as commander in chief must not be questioned in wartime.

Since 9-11, the Bush administration has been trying to expand executive power and to avoid consultation with Congress on issues related to terrorism. The president ignored Congress when he established military commissions to try Gitmo detainees. He ignored existing security law (which Congress would readily have revised) when he set up a massive program of telephone and e-mail surveillance. He has issued about 750 “signing statements” asserting the right to ignore or reinterpret laws that Congress has passed and he has signed.

“There is a strain of legal reasoning in this administration that believes in a time of war the other two branches have a diminished role or no role,” Sen. Lindsay Graham, R-S.C., told the Washington Post.

The crucial message the Supreme Court conveyed to the White House is this: As you battle terrorism, don’t undermine the very democratic institutions you seek to defend.

To which I’d add: Don’t undermine the very democratic system you are promoting abroad. This thought has been much on my mind since returning from a trip to Iran and Iraq.

The White House is vociferously promoting “rule of law” in the Middle East, where religious law often trumps constitutions, and written laws function (or not) at the whim of authoritarian rulers.

In Iran, a supreme cleric has authority that supersedes that of the elected government. In Iraq, the legacy of a brutal dictator makes it painfully hard to establish a workable judicial system, and laws have little meaning for ordinary citizens because they are rarely enforced.

Arabs don’t enjoy separation of powers – our system of checks and balances that keeps (or should keep) an executive from getting out of hand. Parliaments and courts exert minimal leverage against authoritarian rulers. The media are mostly state-controlled, and independent journalists risk prison or worse.

The Hamdan decision is a reminder – for those who never had civics courses in school, or never visited the Middle East – of the importance of checks and balances. As Justice Anthony Kennedy wrote, in a concurring opinion: “Concentration of power in the Executive Branch puts personal liberty in peril of arbitrary action by officials, an incursion the Constitution’s three-part system is designed to avoid.”

The Hamdan decision should make the White House more modest about criticizing other leaders for backsliding on democracy – without first scrutinizing itself. Vice President Cheney recently berated Russian leader Vladimir Putin for restoring authoritarianism. Indeed, Putin advocates “managed democracy,” which means undercutting any institutions that challenge executive power.

The Russian leader has neutered the parliament, changed the elections system for regional governors to one of appointments. And the Russian state now controls national television and most national newspapers. For Putin, democracy means controlling all so-called democratic institutions. Putin also justifies a lot of his behavior by citing the threat of Islamist terrorism on Russia’s borders.

We are not Russia, and Bush isn’t Putin. But the long-running struggle against Islamist extremists, however daunting, cannot justify the degrading of our system.

Justice Sandra Day O’Connor put it brilliantly in a June 2004 case rejecting the president’s claim of authority to hold a U.S. citizen indefinitely as an enemy combatant without a hearing. She wrote: “We have long since made clear that a state of war is not a blank check for the president.

“It is during our most challenging and uncertain moments that our nation’s commitment to due process is most severely tested; and it is in those times that we must preserve our commitment at home to the principles for which we fight abroad.”

The Supreme Court gave us a July Fourth gift by reminding us of those principles. Let the fireworks begin.