As activists marked the 16th anniversary of Guantanamo Bay’s transformation into a military prison with nationwide rallies, a new and disturbing chapter is unfolding in our Kafkaesque experiment with indefinite detention. On Sept. 12, a man, allegedly fighting with ISIS, surrendered to U.S. allies in Syria. He would have been unremarkable, just one of hundreds of alleged ISIS fighters captured that month in Iraq and Syria, except this detainee was a U.S. citizen. Since our perpetual war began in 2001, the U.S. has struggled with how to prosecute detainees captured on foreign battlefields. This U.S. citizen was no different, but also presented his own unique challenges to the U.S. government.

More than two months since the unnamed American was transferred to U.S. control, we seem no closer to deciding how to handle his case. According to media reports, administration officials are debating how to proceed, while the prisoner waits in legal limbo. A federal judge ordered the government to allow the U.S. detainee immediate access to a lawyer in late December. Following that, the American Civil Liberties Union (ACLU) reported that the unidentified American had asked the group to challenge his detention. Still, with each passing day, those of us who protect civil rights (like my own organization, CAIR-NY) are increasingly alarmed at the precedent President Donald Trump is setting through his inaction.

This case could be the most powerful test since World War II of the president’s power to hold Americans without due process or trial. It’s a test of our courts and Congress’s willingness to check the wartime actions of the executive. The debate over military detention is older than our country itself, tracing back to British cases that informed the Framers of the Constitution. In 1330, the British Parliament declared that “no man ought to be adjudged . . . without being arraigned and held to answer . . . when the king’s courts are open.” In 1628, King Charles I was forced to sign the Petition of Right, outlawing arbitrary detention. In 1667, Edward Hyde, First Earl of Clarendon, was impeached for removing political prisoners to “remote and unknown places,” a practice later outlawed by the Habeas Corpus Act of 1679.

These precedents helped inform the U.S. Supreme Court’s analysis in later centuries. In the landmark case ex parte Milliganthe Supreme Court rebuked military commissions for trying civilians outside the battlefield. Decided only a year after the Civil War, the Court in Milligan overturned the death sentence of an Indiana man who was convicted of working as a confederate spy. Writing for a unanimous court, Justice David Davis wrote: “It is the birthright of every American citizen when charged with crime, to be tried and punished according to law.”

Sadly, our courts have not always lived up to this standard. The judiciary was famously mute during World War II, when our military interned more than 120,000 Americans of Japanese descent, most of whom were U.S. citizens. During the same time, the Court issued the infamous decision in ex parte Quirin, affirming the president’s power to try Nazi saboteurs, including American citizens, using military commissions. These dark moments stand as outliers in our broader push for rule of law, and they have been routinely rebuked by jurists and lawmakers in the years since.

In 1971, as the panic of the so-called “Red Scare” ebbed, Congress outlawed exactly the sort of extrajudicial detention we’re seeing in Syria today. 18 USC § 4001 states that no “citizen shall be imprisoned or otherwise detained by the United States except pursuant to an Act of Congress.” Cognizant of our wartime history, Congress made it clear that the president, acting on his own, lacks the power to imprison Americans without trial or due process.

This creates a very different constitutional question from what the courts reviewed in ex parte Quirin, where the Court ruled that Congress had explicitly authorized military commissions. In the aftermath of 9/11, nearly 60 years later, federal courts reached a very different conclusion when they reviewed the detention of José Padilla, an American citizen whom the Bush administration held in military custody.

Padilla was arrested on a material witness warrant as his flight from Zurich landed at Chicago’s O’Hare International Airport in May 2002. An American citizen arrested on U.S. soil, Padilla was held by the Bureau of Prisons in New York City before President George W. Bush ordered him taken into Department of Defense Custody, transferring Padilla to a military prison in South Carolina. Writing only two years after the 9/11 attack, the U.S. Court of Appeals for the Second Circuit found Padilla’s military detention unconstitutional. It was a remarkable decision, even more so coming from a court that sits only blocks from Ground Zero. The Second Circuit ruled that the president lacked a free-standing power to detain U.S. Citizens. As such, military detention could only be done pursuant congressional authorization. Additionally, the Second Circuit found that Congress has done exactly the opposite, prohibiting such detention under 18 USC § 4001. The Supreme Court later dismissed the case on a technicality, and the Fourth Circuit reached a different decision, but the Second Circuit’s core holding was never overturned.

The situation in Syria is further-complicated by the lack of explicit congressional authorization for Trump’s military engagement there. The courts have been willing to grant the president greater leeway when it comes to the treatment of those held “on the battlefield,” but a battlefield presupposes a declaration of war. Rather than support intervention in Syria, Congress repeatedly refused to authorize U.S. engagement when asked by President Barak Obama in 2013 and 2015. Today, our military operations in Syria are being conducted under the guise of the Authorization for the Use of Military Force (AUMF) passed to fight al-Qaeda following the 9/11 terrorist attacks. The terse law empowers the president to “use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001 . . . .”

For years now, the military operations conducted under this AUMF have grown increasingly remote from its stated target. But in Syria, we have clearly moved beyond the scope Congress originally intended for that emergency measure. Today, the U.S. is conducting military operations in a country that had no connection to the 9/11 attacks, against an adversary—ISIS — that didn’t even exist at the time the AUMF was drafted.

Regardless of how one views such military intervention, it’s highly problematic to see it done unilaterally, without congressional authorization. For most of the past century, we have slowly whittled away at Congress’s chief national security power: the declaration of war. If we permit the president to unilaterally define the scope of our foreign military engagements, we let him choose which Americans subject to his stunning military powers of “the battlefield.” Because the president is acting on his own, without congressional approval or a declaration of war, it’s even more crucial for the courts to intervene when necessary. Otherwise, the same logic could easily be used to detain Americans in other foreign countries, or even here at home.

The answer is clear: The American public must demand an end to this unconstitutional detention. Congress must hold oversight hearings to understand how long this prisoner will be held, and how he might be transferred back to the U.S. Defense Department officials must understand that there will be consequences if they continue to blatantly violate the constitutional rights of this suspect. We cannot fight criminals by breaking the law, it will only leave us with a broken constitution.

At the time of writing, Albert Cahn was Legal Director of the New York Chapter of the Council on American-Islamic Relations.

Image: John Moore/Getty