The US Supreme Court on Monday upheld the constitutionality of a federal law that makes it illegal to teach members of a foreign terrorist group how to use peaceful means to pursue political goals.

The statute, outlawing the provision of “material support” to designated terrorist organizations, does not violate free-speech and free-association protections of the First Amendment, and it is not unconstitutionally vague, the majority justices declared.

In a 6-to-3 decision, the high court said the law – part of the USA Patriot Act – is specific enough to provide would-be violators fair notice of when their conduct crosses the line into illegality.

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The majority opinion, written by Chief Justice John Roberts, says that Congress intentionally wrote the statute with a broad sweep to outlaw material support to terror groups in any form, including assistance or expertise that might help nudge the group toward nonviolence.

Chief Justice Roberts quoted a congressional finding in support of his broad reading of the statute: “[F]oreign organizations that engage in terrorist activity are so tainted by their criminal conduct that any contribution to such an organization facilitates that conduct.”

In a dissent, Justice Stephen Breyer said that the majority’s broad reading of the statute raises “grave” doubt about its constitutionality.

“... I would read the statute as criminalizing First-Amendment-protected pure speech and association only when the defendant knows or intends that those activities will assist the organization’s unlawful terrorist actions,” Justice Breyer wrote.

For example, if an aviation expert gave advice that facilitated a hijacking, the expert could be prosecuted for his role in facilitating the hijacking, he said. But teaching leaders of a terror group how to petition the United Nations would not.

Roberts said Congress and the executive branch have rejected this view. Support is fungible, he said: “Such support frees up other resources within the organization that may be put to violent ends.”

He added that diplomatic and legal assistance might help bolster the international image of a terror group that the US considers an enemy.

“In the dissent’s world, such training is all to the good. Congress and the Executive, however, have concluded that we live in a different world,” Roberts said.

The material-support law has been one of the most effective tools in the government’s effort to fight international terrorism. It is designed to isolate extremist groups that use wanton violence for political ends by cutting them off from all potential supporters.

It is also designed to enable prosecutors to act preemptively to disrupt terror plots in the planning stages. The law, broadly interpreted, will make it easier for prosecutors to win convictions against those suspected of helping international terror groups.

Critics have attacked the statute as being so broadly worded that it renders illegal any assistance to a designated terror group – including independent statements of support of a particular group.

The majority opinion says that the First Amendment protects the right of individuals to publicly support – and even join – terror groups. But statements of support must be free of any coordination with terror-group members, the court said.

The decision in Holder v. Humanitarian Law Project stems from a lawsuit filed on behalf of human rights activists who were working with members of the Kurdistan Workers’ Party (PKK) and the Liberation Tigers of Tamil Eelam (LTTE). The PKK is an underground group seeking to establish an independent Kurdish state in southeastern Turkey. The LTTE wants to establish Tamil independence in Sri Lanka. Both groups have carried out terrorist attacks in support of their goals, and both have been designated as terrorist organizations on a US State Department list.

The material-support statute was first passed in 1996 and was later amended as part of the Patriot Act in 2001 and 2004.

Initially, the law was aimed at blocking financial and other types of assistance that might help terror groups carry out acts of terrorism. But after the 9/11 attacks, Congress expanded the statute to make it easier to prosecute individuals seeking to maintain any contact with designated terror groups.

Roughly 150 individuals have been prosecuted under the material-support statute since 2001. So far, about 75 have been convicted, according to the government.

A federal judge in Los Angeles ruled that the law’s use of ill-defined terms like “training” and “service” rendered it unconstitutionally vague. A panel of the Ninth US Circuit Court of Appeals agreed.

The Supreme Court on Monday reversed that holding. Voting with Roberts were Justices John Paul Stevens, Antonin Scalia, Anthony Kennedy, Clarence Thomas, and Samuel Alito.

Breyer’s dissent was joined by Justices Ruth Bader Ginsburg and Sonia Sotomayor.

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