A US appeals court on Wednesday heard arguments over a controversial terrorism law that journalists and scholars worry could be used to lock them up indefinitely for no more than dissent.
The US court in New York heard the case brought by President Barack Obama's administration against a ruling by a federal judge last year that struck down part of the law, known as the National Defense Authorization Act.
In that ruling, Judge Katherine Forrest sided with the activists, including former New York Times journalist Chris Hedges and outspoken academic Noam Chomsky, that the law was vague and could be used to curtail reporters' and other citizens' constitutionally guaranteed right to free speech.
The law gives the military the authority to detain anyone deemed to have links with the September 11, 2001 terrorist attacks that killed nearly 3,000 people, but also anyone "who were part of or substantially supported, Taliban or Al-Qaeda forces or associated forces that are engaged in hostilities against the United States or its coalition partners."
These include "any person who has committed a belligerent act, or has directly supported hostilities."
Bruce Afran, a lawyer for the activists, told a press conference that the law violates the "constitutional barrier" between the military and civilians.
"This case is about guaranteeing that we do not become a society dominated by the military," he said.
In its appeal, the government argues that curtailing the measures would threaten "irreparable harm to national security and the public interest by injecting added burdens and dangerous confusion into the conduct of military operations."
The courtroom was filled to overflowing, while protesters gathered outside to decry what one placard called the "destruction of the First Amendment" of the Constitution, which guarantees free speech.
Hedges, a Pulitzer Prize winner, has said that the so-called Homeland Battlefield provisions suggest "the totalitarian credo of endless war waged against enemies within 'the homeland' as well as those abroad."
Hedges has said that he has cut back on his contacts with individuals in the Middle East for fear that his associations could lead to him being accused of breaking the law.