Last night, with the passage of the Feinstein-Lee amendment to the National Defense Authorization Act (NDAA), we took an important step forward in the cause of ending indefinite detention of Americans. For more than a year, I have worked closely with Senator Feinstein on legislation that would protect Americans’ due process rights and ensure that American citizens and permanent legal residents apprehended on American soil may not be detained without charge or trial. Our amendment garnered overwhelmingly bipartisan support -- including from strong civil libertarians such as myself, Sen. Rand Paul, and Sen. Jim DeMint.

A few who share our commitment to civil liberties have expressed concern that the amendment will not in fact accomplish what it is designed to do. I would like to set the record straight.

The amendment provides: “An authorization to use military force, a declaration of war, or any similar authority shall not authorize the detention without charge or trial of a citizen or lawful permanent resident of the United States apprehended in the United States, unless an Act of Congress expressly authorizes such detention.”

It is the last clause – “unless an Act of Congress expressly authorizes such detention“ – that has been the source of confusion to some friends of individual liberty. They worry that the 2012 NDAA (or perhaps even an earlier Authorization for the Use of Military Force (AUMF)) could be read to provide such an express authorization and thereby satisfy the high bar set forth in our amendment.

In reality, neither the AUMF nor the 2012 NDAA did any such thing. The AUMF contains only broad language giving the President authority to use force against those involved in the 9/11 attacks and does not speak directly to the issue of detention. The 2012 NDAA, which I voted against, provides that the military may detain certain persons under the law of war. But that law also contains an important provision—one we were careful to include in the law—to ensure that the NDAA could not be construed by either the President or the courts as expressly authorizing detention of Americans apprehended on U.S. soil. This provision states: “Nothing in [the NDAA] shall be construed to affect existing law or authorities relating to the detention of United States citizens, lawful resident aliens of the United States or any other persons who are captured or arrested in the United States.”

Because neither the AUMF nor any other law enacted before the 2012 NDAA expressly authorized the detention of Americans apprehended on U.S. soil, and the NDAA cannot be construed to provide the President additional authority with respect to detaining those persons, the Feinstein-Lee amendment accomplishes its purpose and will prohibit detention of Americans apprehended on U.S. soil.

In fact, because the 2012 NDAA did not expressly authorize the indefinite detention of American citizens, the last clause of the Feinstein-Lee amendment is actually critical to enforcing it. No law has expressly authorized indefinite detention of Americans apprehended on U.S. soil, and our amendment ensures that the administration cannot use either the AUMF or the 2012 NDAA to do so.

This is a clear victory for civil libertarians and should be celebrated as a strong step forward in protecting due process rights for all Americans.