AIPAC activists are paying a visit to Washington, D.C., in mid-October, threatening to bring renewed focus on legislation a leading civil liberties group warns will criminalize support for the boycott, divestment, and sanctions (BDS) movement for Palestinian rights.

The American Israel Public Affairs Committee lists support of the Israel Anti-Boycott Act as a key issue in its legislative agenda, asking people to urge their members of Congress to co-sponsor the bill. Several thousand leading AIPAC activists will arrive in Washington beginning October 17.

The American Civil Liberties Union, meanwhile, maintains that the Israel Anti-Boycott Act (S. 720) would have a chilling effect on free speech, as it threatens to penalize U.S. individuals and companies solely on expressed political beliefs. The ACLU opposition reversed the momentum of the legislation, as Democratic senators have been wary of winding up on the opposite side of a central player in the resistance to President Donald Trump.

Democratic Sen. Ben Cardin of Maryland, who introduced the Israel Anti-Boycott Act on March 23, is still working with members to review potential clarifications to the bill, according to his office.

Cardin promised to amend the measure without changing its core function after the ACLU’s legal interpretation of the bill found that violations “would be subject to a minimum civil penalty of $250,000 and a maximum criminal penalty of $1 million and 20 years in prison.”

The ACLU said they will “carefully evaluate” any amendments to the bill to see whether they address concerns.

Following the ACLU announcement, Democratic Sen. Kirsten Gillibrand of New York withdrew co-sponsorship. She said at a town hall in August that she would not support the bill in its current form and called on the authors to change it.

“That directly contradicts the First Amendment, which protects voluntary participation in a political boycott,” ACLU attorney Brian Hauss said. “Even if the bill could be interpreted more narrowly, as some of its supporters claim, its broad language and significant penalties would still chill protected expression by scaring people into self-censorship.”

Cardin continued to defend the bill in a briefing Wednesday, saying the bill does not affect freedom of speech, impose jail sentences, nor penalize individuals for their activities, and the criticisms “are just wrong.”

“We can clarify certain additions that do not change the function of the bill, but will give people more comfort,” Cardin said.

Sen. Chris Van Hollen, D-Md., a reliable supporter of Israel and a respected voice in the party on foreign policy, said recently that he does not support the bill because of the concerns put forward by the ACLU. “My interpretation of that legislation is that it does things that the sponsors say were not intended,” said Van Hollen. “I don’t think any American, for example, should be threatened with fines or imprisonment for expressing their views in the form of participating in economic actions with respect to Israel. I certainly don’t support that bill, certainly in its current form.”

The ACLU has said that even with tweaks to the bill that eliminate the criminal penalties, the civil penalties would still lead to an unconstitutional chilling of speech. The bill also does not distinguish between a boycott of products made in occupied territory versus products made in Israel proper, an aspect of the bill Cardin said will not change. JTA reported Cardin insisted on maintaining the provision “to keep outside actors from imposing a final status solution on Israel absent a peace process.”

There are currently 49 co-sponsors, including 36 Republican senators and 13 Democratic senators.

When The Intercept first reported on the ACLU’s opposition in July, the bill had the backing of 29 Republicans and 14 Democrats.