Sen. Dianne Feinstein, D-Calif.

Earlier this month, the Senate overwhelmingly passed (on a 67-29 vote) my amendment to ban the indefinite detention of U.S. persons – citizens and green card holders – without charge or trial.

Unfortunately, the effects of my amendment have been misrepresented by critics on the left as well as proponents of indefinite military detention on the right, particularly after a handful of senators who previously opposed this effort switched their vote at the last minute.

This unexpected support and the spirited debate on the Senate floor left some with the impression that the amendment was imprecise or a Trojan Horse designed to surreptitiously authorize indefinite detention in the United States.

My amendment is neither, and the legal experts I consulted on the amendment agree.

For example, Steven Vladeck of American University, a law professor who has litigated military detention issues in the Supreme Court and an expert on national security law, testified this year before the Senate Judiciary Committee on this legislation. Professor Vladeck reviewed the statements of support by Senators Carl Levin and Lindsey Graham – both of whom advocated indefinite military detention powers in the past.

Professor Vladeck wrote: “The Graham/Levin colloquy sought to cast [the Feinstein] language as doing exactly the opposite of what it says, i.e., as confirming that U.S. citizens can be detained even within the territorial United States pursuant to the logic of the Supreme Court’s opinion in Hamdi.” Professor Vladeck concluded that Senators Levin and Graham were “exactly wrong” because “the plain text of the bill is simply irreconcilable with that understanding.”

In another article, Vladeck and Georgetown Law Professor Marty Lederman, another expert on military detention and national security, wrote: “If it were to be enacted, the amendment would ensure that a future president could not construe the September 18, 2001 Authorization for Use of Force (AUMF), the FY2012 NDAA, or any comparable statute to authorize the military detention of citizens and LPRs [lawful permanent residents] apprehended within the United States.”

I agree. It is true the courts have previously reached ambiguous and conflicting decisions regarding whether U.S. persons apprehended on American soil may be subject to indefinite detention under the laws of war. However, far from adding to this ambiguity, I am confident my amendment brings much-needed clarification to this area of the law.

My amendment updates the Non-Detention Act of 1971 which Congress passed to repudiate the shameful Japanese-American internment experience during World War II. That landmark legislation, which liberal critics of my amendment have made no effort to overturn, protected only U.S. citizens from detention. In contrast, my amendment broadens protections from indefinite detention, protecting both lawful permanent residents as well as citizens.

At a time when civil liberties are under attack, we should not let the perfect be the enemy of the good. As Professors Lederman and Vladeck note, “The new Feinstein amendment…doesprotect the vast majority of persons in the United States from noncriminal detention without express statutory authorization….”

I would support providing the protections in this amendment to all persons in the United States, whether lawfully or unlawfully present, but we lacked sufficient support in the Senate to do this. Most Republican co-sponsors of the bill said they would not support the legislation if it went that far.

Other critics misrepresent the language of the amendment and charge that it could be read to imply there is an authorization to indefinitely detain illegal immigrants and legal visitors in the United States. In doing this, they ignore the language that explicitly prevents such an interpretation. Again, don’t take my word for it. Professors Lederman and Vladeck say that my amendment “would do nothing of the sort.”

The bottom line: indefinite military detention is incompatible with our values, and this amendment is a major step forward to make sure we never return to the dark chapter of American history when we detained Japanese-American citizens out of fear during World War II.

Dianne Feinstein represents California in the U.S. Senate. Her commentary originally appeared in the Huffington Post.