In what civil libertarians and progressive advocacy groups are denouncing as a "cowardly" sneak-attack on free expression, Sen. Ben Cardin (D-Md.) is reportedly leading a behind-the-scenes bipartisan effort to cram legislation that would criminalize boycotts of Israel into a must-pass omnibus spending package now moving through Congress.

"Hiding anti-BDS legislation in end-of-the-year packages is a cowardly act and one that is being considered only because members of Congress know that this legislation would not pass muster if debated publicly and openly."

—Iram Ali, MoveOn.org

"This is a full-scale attack on Americans' First Amendment freedoms," argued Kate Ruane, senior legislative counsel at the ACLU, which has circulated a petition urging Congress to block the measure. "Political boycotts, including boycotts of foreign countries, have played a pivotal role in this nation’s history—from the boycotts of British goods during the American Revolution to the Montgomery Bus Boycott to the campaign to divest from apartheid South Africa."

Titled the "Israel Anti-Boycott Act," the legislation has stalled in the face of fierce opposition from free speech advocates and Palestinian rights groups, but Cardin is reportedly working with leaders of both parties to exploit the final days of the lame-duck session and ram the measure through with little or public scrutiny.

If passed, the measure would strike a significant blow against the growing Boycott, Sanctions, and Divestment (BDS) movement, which has been endorsed by two newly-elected Democratic members of Congress—Ilhan Omar of Minnesota and Rashida Tlaib of Michigan.

"Regardless of how anyone may personally feel about BDS, Congress' attempts to attach criminal penalties to freedom of expression against the Israeli occupation must not stand," Iram Ali, campaign director at MoveOn.org, said in a statement on Monday. "Hiding anti-BDS legislation in end-of-the-year packages is a cowardly act and one that is being considered only because members of Congress know that this legislation would not pass muster if debated publicly and openly."

When Cardin's bill was introduced in the Senate last year, it was co-sponsored by 42 Republicans, Independent Sen. Angus King (Maine), and 15 Democrats—including Senate Minority Leader Chuck Schumer (D-N.Y.).

"No Democrat who considers themselves to be a progressive—and no member of Congress who claims to defend free speech—should be co-sponsoring any anti-BDS legislation," Ali concluded.

As the ACLU's Ruane noted in a summary of the measure's far-reaching implications for free speech, "knowingly violating the bill could result in criminal financial penalties of up to $1 million."

"Were this legislation to pass, federal officials would have a new weapon at their disposal to chill and suppress speech that they found objectionable or politically unpopular," Ruane concluded. "If the First Amendment means anything, it's that the government cannot suppress political expression it doesn't like."