A group of about 100 activists took to the streets in Chicago Monday morning to rally against " cap-and-trade" legislation approved by the U.S. House of Representatives.

As they marched, protesters carried homemade signs -- "The air is not for sale. No carbon trading," and "Keep the cap, ditch the trade." They chanted, "Coal is over, coal is done, gonna get our power from the sun."

As the group reached the Chicago Climate Exchange in downtown Chicago, about a dozen protesters laid down in the street. Chicago police officers picked them up and put them in a squadron. Other officers moved other activists off the street.

"We are saying no to cap-and-trade. We don't think it's a solution," said Kim Wasserman, coordinator for the Little Village Environmental Justice Organization. "We are demanding just climate change."

Legislation approved by the U.S. House of Representatives and pending in the Senate would cap greenhouse gas emissions and let companies trade the right to pollute. Cleaner companies would be able to sell credits, or pollution allowances, to dirtier firms as long as they all stayed below the national limit.

Critics, including those taking part in the protest, argue the system would overly benefit polluters and not do enough to limit climate change.