Here is the 6-3 opinion in Holder v. Humanitarian Law Project, upholding the federal law that bars "material support" to groups designated as "foreign terrorist organizations," including advice or advocacy for nonviolent, peaceful, lawful ends. An excerpt from the majority (authored by Chief Justice Roberts) follows below:
Congress has prohibited the provision of “material support or resources” to certain foreign organizations that engage in terrorist activity. 18 U. S. C. §2339B(a)(1). That prohibition is based on a finding that the specified organizations “are so tainted by their criminal conduct that any contribution to such an organization facilitates that conduct.” Antiterrorism and Effective Death Penalty Act of 1996. ... The plaintiffs in this litigation seek to provide support to two such organizations. Plaintiffs claim that they seek to facilitate only the lawful, nonviolent purposes of those groups, and that applying the material-support law to prevent them from doing so violates the Constitution. In particular, they claim that the statute is too vague, in violation of the Fifth Amendment, and that it infringes their rights to freedom of speech and association, in violation of the First Amendment. We conclude that the material-support statute is constitutional as applied to the particular activities plaintiffs have told us they wish to pursue. We do not, however, address the resolution of more difficult cases that may arise under the statute in the future.