Half of the states have responded to the BDS movement by boycotting the boycotters, refusing to hire contractors who won’t promise not to shun companies that do business in Israel. The Combating BDS Act, a bill introduced in the U.S. Senate last week, aims to protect such laws by eliminating the threat of federal pre-emption.

The American Civil Liberties Union has successfully challenged anti-BDS laws on behalf of a curriculum coach in Kansas and an attorney in Arizona, and last month the Council on American-Islamic Relations filed a similar lawsuit on behalf of a speech pathologist in Texas. The ACLU and CAIR argue that rejecting contractors who refuse to sign an anti-boycott pledge unconstitutionally punishes them for exercising their First Amendment rights.

All three lawsuits rely on a 1982 case in which the Supreme Court said an NAACP boycott of white merchants in Claiborne County, Mississippi, aimed at securing “compliance by both civic and business leaders with a lengthy list of demands for equality and racial justice,” was protected by the First Amendment. Last year two federal judges agreed that the BDS movement is constitutionally analogous to the NAACP boycott and issued preliminary injunctions against enforcement of anti-BDS laws in Kansas and Arizona.