A Denver protest Saturday over fears extremist interpretations of Islamic law will one day become the law of the land ended up producing yelling and insults, some scuffles and at least four arrests.

The Denver rally was one of more than two dozen held in American cities Saturday, organized by ACT for America, which claims Islamic law — namely Shariah — is incompatible with Western democracy. Protesters at the western steps of the State Capital claimed Shariah calls for the abuse of women and has no place in America.

They said liberals, Democrats and others are allowing Shariah to supplant the U.S. Constitution.

“I don’t understand why they want this,” said one woman, who declined to give her name. She was looking at a group of counter-protesters gathered at the sidewalk skirting Broadway.

Colorado State Troopers and Denver Police put up yellow tape around the capitol steps to keep the two sides well away from each other. Each side boasted about 150-to-175 people.

Using bullhorns, they taunted each other for about two hours under a sweltering sun. About 5 p.m.the anti-Shariah group began walking through Civic Center park, surrounded by police and yelling counter-protesters.

There were some quick confrontations and police made four arrests. Police then cleared the park while counter-protesters yelled at them.

The same basic scene was repeated in other cities throughout the country Saturday, with most confrontations happening as the protests ended.

At a park near New York courthouse, counter-protesters sounded air-horns and banged pots and pans in an effort to silence an anti-Shariah rally. In St. Paul, Minn., state troopers arrested about a half-dozen people when scuffles broke out at the close of a competing demonstration.

An overwhelming majority of Muslims don’t want to replace U.S. law with Shariah, and only “radical extremist groups” would call for that, Liyakat Takim, a professor of Islamic students at McMaster University in Hamilton, Canada, told the Associated Press.

In fact, Shariah refers to guidelines or principles that are shared among Muslims while “Fiqh” refers to jurisprudence, or specific laws, which can change, said Takim.

“The Quran allows slavery. So does the Old Testament. That doesn’t mean we allow it today too,” Takim said. “Laws are amenable to change.”

Still, Denver resident Stephanie Potts said most Americans need an education on the contradictions between Shariah and American law. She handed out copies of her research Saturday.

“I appreciate what the left is trying to do to boost multiculturalism,” said Potts. “But they have never picked up a Quran and they don’t understand that Islam is not about multiculturalism.”

The protest did prompt Nishika Ramaswami to hold a sign supporting Muslims. A native of India, Ramaswami said she was dismayed about the level of distrust Islam generates in the United States.

“I think it’s ridiculous in this day and age to be protesting a religion,” she said. “It just doesn’t make sense.”

The Associated Press contributed to this report