In American law, providing material support for terrorism is a crime prohibited by the USA PATRIOT Act and codified in title 18 of the United States Code, sections 2339A and 2339B. It applies primarily to groups designated as terrorists by the State Department. The four types of support described are “training,” “expert advice or assistance,” “service,” and “personnel.” In June 2010, the United States Supreme Court upheld the law in an as-applied challenge in the case Holder v. Humanitarian Law Project, but also left open the door for other as-applied challenges. The plaintiffs in the case had sought to help the Kurdistan Workers' Party in Turkey and the Liberation Tigers of Tamil Eelam learn means of peacefully resolving conflicts.
The material support provisions have been criticized by rights groups as violating the First Amendment, as they criminalize activities like the distribution of literature, engaging in political advocacy, participating in peace conferences, training in human rights advocacy, and donating cash and humanitarian assistance, even when the support is intended only to promote lawful and non-violent activities. The provisions are vague and wide-ranging, and impose guilt by association by punishing people not for their own acts but for the acts of those they have supported. The Secretary of State's power to designate groups as terrorist has also been criticized as being too broad, giving the Executive too much discretionary power to label groups as "terrorist" and criminalize their supporters. The American Civil Liberties Union note that: “Federal “material support” and conspiracy statutes allow the government to secure convictions without having to show that any specific act of terrorism has taken place, or is being planned, or even that a defendant intended to further terrorism.”