Congress is debating whether to rush through a controversial bill that fines US companies and their employees for participating in internationally organized boycotts of Israel or its West Bank settlements by the end of the year.

Sen. Ben Cardin, D-Md., is seeking to attach the Israel Anti-Boycott Act to must-pass spending legislation, The Intercept reported today. The bill takes aim at the pro-Palestinian boycott, divestment and sanctions (BDS) movement.

But adding it to an unrelated spending bill may be a hard sell, even among supportive Republicans. And many Senate Democrats remain wary of backing the bill due to constitutional concerns raised by civil liberties groups. The American Civil Liberties Union (ACLU) sent a letter to the Senate today asking lawmakers not to include the bill in spending legislation.

“We want to keep as many legislative riders off the appropriations bill, whatever they are, if we can,” Senate Appropriations Committee Chairman Richard Shelby, R-Ala., who co-sponsored the bill, told Al-Monitor. “We’ve been pretty successful thus far, but it’s not over with yet.”