By Senator Dianne Feinstein

One of the fundamental principles of American democracy, dating back to the Bill of Rights, is due process of law.

So it came as a shock to many when the Senate failed to reaffirm that right during debate this month over whether American citizens — even those captured on U.S. soil — can be detained indefinitely without charge or trial.

My Senate colleagues would be well served to look back 70 years to the last time our government approved indefinite detention of American citizens.

On Feb. 19, 1942, President Franklin Roosevelt signed an executive order relocating 120,000 people of Japanese ancestry — the majority U.S. citizens — to internment camps.

When I was a child, my father took me to the Tanforan Racetrack near San Francisco. The track was a “Civilian Assembly Center,” a staging point for detainees en route to more permanent “Relocation Centers” in rural California, Arizona and Utah.

Seeing the barbed wire, finding the detainees housed in horse stables and small buildings on the infield, was a singular experience in my life. Years later, the events remain a dark stain on our history.

In 1971, after repealing a 1950 law that explicitly allowed detention of citizens, President Nixon wrote: “Our democracy is built upon the constitutional guarantee that every citizen will be afforded due process of law.”

Sometimes, however, even the most shameful acts of government fade too quickly from our national consciousness. During Senate debate over the National Defense Authorization Act this month, there was fierce argument to reinstate a policy of indefinite detention of American citizens.

In the end, the Senate adopted a compromise amendment, leaving it to the courts to decide whether American citizens captured inside the United States can be held without charge or trial.

Proponents of indefinite detention point to the case of Yaser Esam Hamdi, a citizen detained as an enemy combatant in Afghanistan. In Hamdi vs. Rumsfeld, the U.S. Supreme Court affirmed that Hamdi could be designated an enemy combatant.

But the decision was far from clear. Four justices limited the opinion only to citizens captured outside the United States and held that Hamdi was entitled to due process. Four other justices would have held that the government lacked authority to hold Hamdi in detention.

Faced with this muddled result, the Bush administration chose to end Hamdi’s detention and release him to Saudi Arabia, on the condition that he relinquish his U.S. citizenship.

Another case to consider is that of Jose Padilla, a U.S. citizen captured in Chicago and accused of plotting to detonate a “dirty bomb.” Declared an enemy combatant, Padilla was held without charge in a military prison for three years.

Amid considerable criticism, he was transferred to civilian federal court and convicted.

The argument is not whether citizens such as Hamdi and Padilla — or others who would do us harm — should be captured, interrogated, incarcerated and severely punished. They should be.

But what about an innocent American? What about someone in the wrong place at the wrong time? The beauty of our Constitution is that it gives every citizen the basic due process right to a trial on their charges.

Experiences over the last decade prove the country is safer now than before the 9/11 attacks. Terrorists are behind bars, dangerous plots have been thwarted. The system is working.

We must clarify U.S. law to state unequivocally that the government cannot indefinitely detain American citizens inside this country without trial or charge.

The federal government experimented with indefinite detention of U.S. citizens during World War II, a mistake we now recognize as a betrayal of our core values.

Let’s not repeat it.