Editor’s Note: This column was co-authored by Bob Morrison

President Obama took the oath of office on Tuesday, January 20, 2009. In that Abraham Lincoln Bicentennial year, Mr. Obama sought to stress his admiration for the only other president from Illinois. Millions of people watched as he placed his left hand on the Lincoln Bible and raised his right hand. Around the world, billions viewed the event on television. On the National Mall, army howitzers of the Presidential Salute Battery fired off a 21-gun salute to honor the new commander-in-chief.

It was surely a great day for all Americans. Nearly 400 years before, a single Dutch ship had brought chained Africans to Jamestown in the colony of Virginia, thus beginning centuries of slavery and oppression. President Obama was right to see the transcendent meaning in his elevation to the highest office in the land.

That is why his contempt for law is so deeply troubling. We understand that he rejects the Defense of Marriage Act and views it as unconstitutional. Still, until it is repealed, or until it is deemed by our courts–including the highest court – to be unconstitutional, he has taken an oath to “faithfully execute the office of President of the United States.” The Constitution that he swore before God to “preserve, protect, and defend” requires the president to “take care that the laws be faithfully executed.” Not just the laws he approves of, not merely those laws he would have voted for as a legislator, but the laws.

Lincoln taught Americans to reverence the laws. He broke with the abolitionists of his day over the hateful Fugitive Slave Act. Lincoln hated that law, too, but he said we had to obey it because the Constitution provided for it. We had to obey that law, Lincoln wrote his dearest friend, slaveholder Joshua Speed of Kentucky, even though “we crucify our feelings” in so doing. Crucify our feelings. What a phrase.

Why is it important for President Obama to obey and to enforce the law? Because reverence for the laws is one reason those army howitzers fired blanks into the chill noon air – and not at the White House. How many other republics have seen their constitutions and their liberties crushed under tank treads? Our national reverence for law and our military’s respect for civilian authority are two more of the many, many things that make America exceptional among the nations.

There are serious consequences for failure to take care that the laws be faithfully executed. In 1974, the Judiciary Committee of the House of Representatives voted three articles of impeachment against President Richard Nixon. Article III charged Nixon with “failure to take care that the laws be faithfully executed.” Once the Nixon White House tapes were handed over, under order of the Supreme Court, Republicans and Democrats together demanded Nixon’s ouster. No one could deny that a two-year secret campaign of denial, diversion, and obstruction of justice had resulted in, at the very least, a failure to take care that the laws be faithfully executed. Nixon was soon forced to resign.

No one is suggesting that Mr. Obama’s defiance of law will result in his defeat or in his impeachment. What we are suggesting is that he does grave harm to the power and legitimacy of his own high office by his contempt for law. As a former constitutional law professor, he should be the first to uphold the majesty of the law.

We appeal to President Obama: Be true to the Oath you swore on the Lincoln Bible.

You spoke before a cloud of witnesses. We urge you, Mr. President, to maintain respect for law. If you conscientiously disagree with the Defense of Marriage Act, then seek its repeal through proper legislative and judicial channels.

Of course, we will oppose that repeal. We believe that the laws of nature and of nature’s God, so powerfully invoked by our Declaration of Independence, support the civil right of marriage. True marriage is an institution that existed before the republic.

It will be a tragedy of historic proportions if this president, of all presidents, is the one to overturn the civil right of marriage. In 1866, thousands of freedmen and women walked to Tennessee. Many of them walked barefooted. Why? They desperately sought to have their slave marriages recognized in law. Those newly freed Americans understood the civil right of marriage better than do many constitutional law professors today. Let’s preserve marriage. And let’s take care that the laws that defend it be faithfully executed.