The United States Constitution is the law of the land. Our nation’s founding charter was intended to reflect our British common law heritage, the lessons of Greek democracy, and the principles of the Roman Republic. It contains historic civil liberties protections that date back to the Magna Carta.

The founders were keen on making sure the federal government’s powers were limited and few, and given their recent experience with King George III, they made a particular point to balance and restrain the power of the executive branch. Unlike in other countries and certainly unlike in 18th-century England, in America even the head of state would not be above the law.

At the time, many observers saw our Constitution as the crowning achievement of the West. It was the grand culmination of philosophies on governance that spanned centuries. It wasn’t simply a statement of law; it was an affirmation of proper civilization.

President Obama has never seemed too bothered by constitutional restraint. To be fair, neither have most of his modern predecessors, who steadily expanded executive power far beyond its constitutional bounds. Liberals viewed President George W. Bush as one the worst enemies of civil liberties, because he supported legislation such as the Patriot Act, policies such as indefinite detention, and legal redefinitions of torture. Yet despite promising “change,” Obama has maintained most of Bush’s anti-civil liberties policies, even expanding them in some cases.

Now, Obama has lowered the bar even further. When American-born al Qaida collaborator Anwar al-Awlaki was assassinated by a U.S. drone strike in Yemen last week, The New York Times noted that “it is extremely rare, if not unprecedented, for an American to be approved for targeted killing.” There is little question that al-Awlaki was as bad as most reports indicated. He was inspiring radical jihadists to take up arms against the United States. There is also little question that the war against radical Islamists is a war unlike any other in our country’s history.

The problem with killing al-Awlaki is the precedent it sets. If President Obama’s overall domestic and foreign policies weren’t already bad enough, he has now taken the United States to a new civilizational low by undermining the most basic purpose and precept of American law: the protection of citizens’ rights through due process.

When, in 2004, the Supreme Court ruled against a father who was seeking constitutional protections for his American-citizen son who had been imprisoned as an enemy combatant without charge or trial, conservative Justice Antonin Scalia dissented, arguing: “Where the Government accuses a citizen of waging war against it, our constitutional tradition has been to prosecute him in federal court for treason or some other crime …”

Obviously Scalia believes our Constitution and legal traditions should have some bearing on such matters. Later in his dissent, Scalia quoted 18th-century British judge Sir William Blackstone, widely considered to be an authority on English common law:

The very core of liberty secured by our Anglo-Saxon system of separated powers has been freedom from indefinite imprisonment at the will of the Executive. Blackstone stated this principle clearly: “Of great importance to the public is the preservation of this personal liberty: for if once it were left in the power of any, the highest, magistrate to imprison arbitrarily whomever he or his officers thought proper … there would soon be an end of all other rights and immunities. … To bereave a man of life, or by violence to confiscate his estate, without accusation or trial, would be so gross and notorious an act of despotism, as must at once convey the alarm of tyranny throughout the whole kingdom. …”

It’s easy to imagine what liberals would have said if George W. Bush had ordered the assassination of al-Awlaki — certainly “despotism” and “tyranny” would’ve been some of the more pleasant words thrown around. But while Bush was rightly criticized for imprisoning some citizens without due process, Obama is now applauded for killing them.

As of this writing, Reuters is reporting that “American militants like Anwar al-Awlaki are placed on a kill or capture list by a secretive panel of senior government officials, which then informs the president of its decisions, according to officials. … There is no public record of the operations or decisions of the panel … Neither is there any law establishing its existence or setting out the rules by which it is supposed to operate.”

The “alarm of tyranny” “throughout the kingdom” Blackstone spoke of, Scalia cited, and our Constitution was designed to prevent is now one step closer to reality, as President Obama nonchalantly oversteps his legal authority to the applause of many and the concern of few.

Perhaps killing al-Awlaki without due process was necessary given the circumstances. But the question isn’t whether extraordinary circumstances sometimes require extra-constitutional measures. The question is why there is no question.

Jack Hunter writes at the “Paulitical Ticker,” where he is the official Ron Paul 2012 campaign blogger.