Ed Shanahan, executive director of MCFL, advised people to go to the www.federalregister.gov where the federal administration has posted a proposal entitled "Certain Preventive Services Under the Affordable Care Act" with a 90-day public comment concerning the mandate.

"I think it is imperative that people learn about this mandate," he said.

"That is the opportunity for the American people to express their concern with each and every aspect of the 'Obamacare Mandate' with which they have a concern. As good Christians, as good followers of any religion for that matter, we should all be overrun with concerns about what this mandate means for religious freedom across the country," Shanahan said.

According to the national website "Stand Up For Religious Freedom," the protesters joined 54,000 across the United States at noon that day to protest the mandate.

Some Catholics at the Boston rally shared their reasons for making a stand for their faith in a public venue.

Christopher Oravetz, 27, of Cambridge attends Mass at St. Francis Chapel in the Prudential Center. He said young people need to stand up on issues like the mandate, to protect their religious freedom publicly.

"For young people, I think it is important that as we grow and enter into our future vocations -- whether it be marriage, a call to religious life, or celibate life -- that we be responsible for taking an active civic role within our communities, within our families, within our state. It is important for us to be educated now," Oravetz said.

U.S. Air Force veteran Frank Nealon, 83, of St. Mary's Parish in Milford and Kathy Riordan, 59, of St. Agatha's Parish in Milton held the banner behind the speakers during the rally.

"We have to stand up for our religion. That is the duty of the lay faithful. The priests and the cardinal cannot do this alone. We have to stand up and exercise our baptismal and confirmational character. So, I am very proud to stand here," Riordan said.