One of the two statewide ballot initiatives passed by voters in November now faces a pair of legal challenges from groups and individuals arguing it violates the U.S. Constitution by limiting free speech.

The amendment prohibits political gifts by holders of contracts worth $100,000 or more if the government awards them without a competitive bidding process.

But the ban extends to officers and board members of companies and nonprofits, as well as unions that represent government workers and their family members.

Among the parties filing one of the lawsuits against Amendment 54: Children's Hospital, the University of Denver, Dan Ritchie of the Denver Center for the Performing Arts and Oakwood Homes CEO Patrick Hamill. Denver City Councilman Charlie Brown also signed on as a plaintiff because he would no longer be able to contribute to his own re-election campaign if he continues to serve on the board of Visit Denver, the city's convention and visitors bureau.

"We think participation in the political process is a fundamental right," said Greenberg Traurig's Doug Friednash, one of the attorneys handling the case.

A group of labor unions, including Aurora firefighters, Douglas County teachers and other officials, mounted its own legal challenge at the same time in Denver District Court.

The labor-backed challenge, led by Denver attorney Mark Grueskin, also argues the political gift ban violates the 14th Amendment by treating labor organizations' political committees differently from those formed by other government contractors, which can continue to make contributions.

The amendment's proponent, Tom Lucero, predicted his measure would withstand scrutiny by the courts. "Campaign finance restrictions are indeed legitimate to the extent they are narrowly tailored to prevent corruption, and that's exactly how Amendment 54 was designed," Lucero said in a statement.

Legal experts have been arguing that the narrowly approved Amendment 54 casts too wide a net because it not only bans political contributions by everyone from union members to prominent business leaders but also extends to family members.

Children's Hospital objects to the amendment because it could lose its state contracts if any of its board members or their family members inadvertently give money to a political candidate or issue.

The specialty hospital has state Medicaid contracts to provide services not available from any other health care facility. Some of its board members have considered resigning.

"Amendment 54 could have catastrophic repercussions for children throughout Colorado," Children's CEO Jim Shmerling said in a statement. "It would be devastating if that care was jeopardized."

DU, which conducts research and provides other services to the government under contract, has expressed similar concerns about attracting and retaining community leaders to serve on its board if they are prohibited from making political contributions to any candidate or issue.