Writing for the majority, Justice Samuel A. Alito Jr. said that the journalists, lawyers and human rights advocates who challenged the constitutionality of the law could not show they had been harmed by it and so lacked standing to sue. The plaintiffs’ fear that they would be subject to surveillance in the future was too speculative to establish standing, he wrote.

Justice Alito also rejected arguments based on the steps the plaintiffs had taken to escape surveillance, including traveling to meet sources and clients in person rather than talking to them over the phone or sending e-mails. “They cannot manufacture standing by incurring costs in anticipation of nonimminent harms,” he wrote of the plaintiffs.

It is of no moment, Justice Alito wrote, that only the government knows for sure whether the plaintiffs’ communications have been intercepted. It is the plaintiffs’ burden, he wrote, to prove they have standing “by pointing to specific facts, not the government’s burden to disprove standing by revealing details of its surveillance priorities.”

In dissent, Justice Stephen G. Breyer wrote that the harm claimed by the plaintiffs was not speculative. “Indeed,” he wrote, “it is as likely to take place as are most future events that common-sense inference and ordinary knowledge of human nature tell us will happen.”

Under the system of warrantless surveillance that was put in place by the Bush administration shortly after the terrorist attacks of Sept. 11, 2001, aspects of which remain secret, the National Security Agency was authorized to monitor Americans’ international phone calls and e-mails without a warrant.