The high court left intact a July 2013 2nd U.S. Circuit Court of Appeals decision that journalists and others who said they could be detained under the law, did not have standing to sue.
The provision in question is part of the National Defense Authorization Act, which the U.S. Congress passes annually to authorize programs of the Defense Department.
It lets the government indefinitely detain people it deems to have "substantially supported" al Qaeda, the Taliban or "associated forces."
Journalists and activists whose work relates to overseas conflicts, including Pulitzer Prize winner Chris Hedges and an Icelandic spokeswoman for the Wikileaks website, said that the law could subject them to being locked up for exercising constitutionally protected rights. They also said the threat of enforcement violated their right to free speech.
In September 2012, U.S. District Judge Katherine Forrest of New York issued a permanent injunction preventing the United States from invoking the part of the law authorizing indefinite detentions.
The appeals court said the challengers had no standing because they could not show the provision has any bearing on the government's authority to detain U.S. citizens.
The court said the plaintiffs who were not U.S. citizens lacked standing to sue because they did not show "a sufficient threat that the government will detain them" under the provision.
The case is Hedges v. Obama, U.S. Supreme Court, No. 13-758