The American Civil Liberties Union (ACLU) wrote to members of Congress this week to warn them that a piece of legislation gaining steam in the House and Senate, aimed at protecting Israel from any economic boycotts, was a flat-out violation of the United States constitution. While at least one House sponsor, Rep. Joe Kennedy III (D-MA), has already said he will review the bill in light of the group’s concerns, so far none of the 46 Senate or 238 House sponsors and co-sponsors has withdrawn support — even those who have been the most fervent critics of other restrictions on speech.

Known as the Israel Anti-Boycott Act, the legislation would expand existing laws to prohibit Americans from “requesting the imposition of any boycott by a foreign country against a country which is friendly to the United States” and from “supporting any boycott fostered or imposed by an international organization, or requesting imposition of any such boycott, against Israel.” According to the ACLU’s letter, this would mean penalties — including up to 20 years in prison and fines between $250,000 and $1 million — for advocating for or even requesting information about a boycott of the state of Israel.

While the bill has attracted both Democratic and Republican support, some of the people who have signed on to this bill have been among the most vocal critics in the past of other measures they considered to be limiting to free speech.