The National Rifle Association filed a lawsuit Wednesday challenging a newly implemented ordinance by the city of Los Angeles that seeks to limit ties between city contractors and the gun rights group.

The lawsuit alleges that the ordinance, which took effect on April 1, violates constitutional protections for free speech and association under the First Amendment and the right to equal protection under the 14th Amendment.

Under the ordinance, city contractors are required to fully disclose any sponsorship of, or contract with, the NRA. It was approved unanimously by the Los Angeles City Council in February. It allows the city to terminate a contract if the contractor does not disclose all ties with the NRA.

The ordinance cites the NRA's blocking of "sensible gun safety reform" even in the aftermath of several mass shootings in the U.S. It says public funding provided to contractors with ties to the NRA "undermines the City's efforts to legislate and promote gun safety."

"I support this policy, I'm confident in it, and we're not going to be bullied by the NRA," said Mayor Eric Garcetti in an emailed statement.

Other supporters of the ordinance called the NRA's lawsuit "desperate."

"The NRA's First Amendment rights remain firmly in place while the City chooses to exercise its own rights to require disclosing who has ties to the NRA, so residents of Los Angeles know how and where their tax dollars are being spent," said council member Mitch O'Farrell, who originally introduced the measure, in an emailed statement.

In its lawsuit, the NRA claims the city is bringing political pressure to bully companies that support the group.

"The Ordinance has nothing to do with awarding contracts to the best candidates, fiduciary stewardship of public resources, or providing equal and open opportunities," according to the lawsuit. "Instead, it is about discriminating against a lawful organization and its members and supporters because the City does not approve of their political speech."

NRA attorney Chuck Michel said individuals who contract with city will be forced to choose between their NRA memberships or having their businesses placed on "this blacklist."

"This is modern-day McCarthyism, and my clients are confident no judge will let it stand," said Michel in an emailed statement.

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