A bill that would set up a government commission to study U.S.-based terrorism was the target of a protest by civil libertarians Tuesday in downtown Portland.

The measure, sponsored in the Senate by Sen. Susan Collins, R-Maine, would establish a 12-member commission to examine and report on what the bill calls “violent radicalization,” “homegrown terrorism” and “ideologically based violence.”

But to the speakers at Tuesday’s rally, the proposed government panel is reminiscent of the House Un-American Activities Commission, which investigated suspected Communists during the 1950s and is now seen widely as part of a shameful chapter in U.S. history.

The protesters expressed concern that what they described as vague language could put many people in the government’s crosshairs.

Shenna Bellows, executive director of the Maine Civil Liberties Union, said the bill sends a message that political dissent and radical ideology are dangerous.