When the San Francisco Board of Supervisors declared the National Rifle Association a "domestic terrorist organization" on Tuesday, it also said "the City and County of San Francisco should take every reasonable step to assess the financial and contractual relationships our vendors and contractors have" with the NRA. After that assessment, it said, city officials "should take every reasonable step to limit those entities who do business with the City and County of San Francisco from doing business with this domestic terrorist organization."

While the resolution is nonbinding, attempts to follow through on that threat could be unconstitutional. As Reason Contributing Editor Walter Olson notes, the Supreme Court ruled in 1996 that "the First Amendment protects independent contractors from the termination of at-will government contracts in retaliation for their exercise of the freedom of speech." That case, Board of County Commissioners v. Umbehr, involved a trash hauler who complained that his contract with Wabaunsee County, Kansas, had been terminated because he had publicly criticized the county commissioners.

The principle that Umbehr established poses a problem for San Francisco's NRA-shunning efforts. As Washington Post columnist Henry Olsen observes, San Francisco's aspiration to avoid contractors tainted by the NRA "arguably sets the power of a government against a set of citizens solely on the basis of their politics."

If the city were paying the NRA for firearms training and decided to end that arrangement because of the organization's Second Amendment advocacy, that decision would be clearly analogous to what the Waubansee County commissioners were accused of doing. More realistically, if the city starts to cut off contractors because of their ties to the NRA, that policy could implicate the contractors' First Amendment rights.

Any contractors who are NRA members, for instance, have a "financial relationship" with the organization by virtue of the dues they pay. If financial relationships with this "domestic terrorist organization" disqualify people from doing business with the city, that policy would punish NRA members for exercising their First Amendment rights. Or imagine a printer who does work for the NRA at a discounted rate because he agrees with the organization's goals. If the city stopped hiring the printer because of his "financial and contractual relationships" with the NRA, it would likewise be discriminating against him based on his political views.

San Francisco's anti-NRA stance is reminiscent of New York Gov. Andrew Cuomo's attempts to bully state-regulated banks and insurers into shunning the group. Last year a federal judge allowed the NRA's First Amendment lawsuit challenging Cuomo's intimidation campaign to proceed. U.S. District Judge Thomas McAvoy concluded that the governor seemed to be sending "the message that insurers and financial institutions that do not sever ties with the NRA will be subject to retaliatory action by the state."

That is not cool under the First Amendment. "However controversial it may be, 'gun promotion' advocacy is core political speech entitled to constitutional protection," McAvoy noted. He ruled that the state's regulatory guidance to banks and insurers, combined with Cuomo's public comments about the NRA, "provides a sufficient basis to invoke the First Amendment."

However that case turns out, Umbehr seems directly relevant to San Francisco's anti-NRA campaign as it relates to city contractors. "We recognize the right of independent government contractors not to be terminated for exercising their First Amendment rights," the Supreme Court said. San Francisco's supervisors seem to have overlooked that right, possibly because they equate opposition to gun control with terrorism.