NEW YORK — A federal appeals court in Manhattan has revived enforcement of a law that permits the indefinite detention of people suspected of supporting terrorists, saying a lower court mistakenly ruled for plaintiffs who opposed it.

The 2nd U.S. Circuit Court of Appeals issued the ruling Wednesday in a lawsuit challenging the law that allows the U.S. government to detain anyone who "substantially" or "directly" provides "support" to radical forces, such as al-Qaida or the Taliban. The court found that the plaintiffs had no standing to bring the case in the first place.

In response to the decision, a lawyer for the plaintiffs, Bruce Afran, accused the appeals court of failing to address the merits of the case by instead reversing the lower court's decision on technical grounds. A spokeswoman for the U.S. Attorney's Office in Manhattan had no comment.

The decision sent the case back to the district court to let the judge consider further proceedings. But Afran said it was unclear whether that would happen.

In a ruling last year, U.S. District Judge Katherine Forrest found that the law was "unconstitutionally overbroad." She urged Congress to make it more specific so journalists, scholars, political activists and others would not worry that contacting enemies of the United States would put them in jeopardy of indefinite incarceration.

"First Amendment rights are guaranteed by the Constitution and cannot be legislated away," Forrest wrote. "This court rejects the government's suggestion that American citizens can be placed in military detention indefinitely, for acts they could not predict might subject them to detention."

The appeals court found that the plaintiffs who are U.S. citizens, including Pulitzer Prize-winning journalist Christopher Hedges, "do not have standing to challenge the statute" because the relevant section "simply says nothing about the government's authority to detain citizens."

Other plaintiffs, including foreign political activists, also failed to show they had ground to fear the law, even though it "does have meaningful effect regarding the authority to detain individuals who are not citizens or lawful resident aliens," the appeals panel said.

Hedges has interviewed al-Qaida members, mixed with members of the Taliban during speaking engagements overseas and reported on 17 groups named on a list prepared by the State Department of known terrorist organizations. He testified that the law has forced him to consider altering speeches where members of al-Qaida or the Taliban might be present.

Government lawyers had argued that the fears of journalists and others were unfounded. They claimed that the 2011 statute simply reaffirms powers authorized by Congress after the Sept. 11, 2001, terror attacks.

But Afran said the appeals court decision "follows a disturbing and dangerous trend in which the federal courts are refusing to address the merits of civil liberties cases. It sends a message that you can't go to court unless the military is knocking at your door ready to take you into custody."