Missouri lawmakers have never hidden their distaste for Obamacare. Besides sitting out the Medicaid expansion and refusing to set up a state-run marketplace for health insurance, Missouri has enacted some of the nation’s toughest restrictions on “navigators,” the community workers paid by the federal government to help consumers find affordable coverage.

Now health advocates are calling the state’s bluff. In a lawsuit filed in federal district court last week, physicians and community organizations claim that Missouri’s “Health Insurance Marketplace Innovation Act of 2013” violates both federal law and the U.S. Constitution.

Under the Affordable Care Act, the federal government trains, tests and certifies health care navigators. States can subject navigators to additional regulations, as long as the rules don’t “prevent the application” of the health care law. The lawsuit claims Missouri crosses that line by restricting what navigators can say to consumers and limiting what the rest of us can say to each other. Some examples:

● The Missouri law bars navigators from offering “advice concerning the benefits, terms, and features of a particular health plan.” Yet their job, under federal law, is to help people find and choose the plans that are best for them.

● Missouri prohibits navigators from talking about plans sold outside of the state’s federally-operated insurance exchange—yet the health care law requires them to “provide information about the full range of qualified health plans.”

● If a Missouri navigator meets a consumer whose current health plan was purchased through a private insurance broker, the navigator must refer the consumer back to the broker. Brokers are paid to push certain companies’ products, but federal law requires navigators to provide “impartial information” and “act in the best interest of the applicant.”

● The Constitution bars lawmakers from regulating the content of speech, but the Missouri law effectively prohibits anyone from sharing advice about health insurance, even casually, without first getting licensed as a navigator.

Two of the plaintiffs in the lawsuit—the St. Louis Effort for AIDS and Planned Parenthood of the St. Louis Region—have been certified and licensed by the state. But the lawsuit claims the state is keeping them from performing their federally assigned roles. “Planned Parenthood has received numerous questions from individuals, including whether there are differences between the plans that are offered on the Exchange … and whether there are any products a person should consider off the Exchange,” the complaint says. “Planned Parenthood believes that it cannot answer these questions because under [the Missouri law], it is not allowed to discuss the benefits, terms and features of health plans or to talk about products not offered on the Exchange.”

Two other plaintiffs—the Consumers Council of Missouri and Missouri Jobs with Justice—say they can’t even sustain their routine activities without running afoul of the state’s onerous restrictions. Neither group employs official navigators, but both work to promote affordable health care and help people find it. “Consumers Council believes that it cannot provide Missourians with information about enrollment because performing these duties could be performing ‘service as a navigator,’” the complaint alleges, “and thus the [council] could be penalized for doing so without a license.”

The other plaintiffs—two retired physicians, a social welfare advocate and a cerebral palsy patient named Chris Worth—voice related concerns. “Chris Worth would like to make an educated choice about which plan to choose and believes that the health care attorneys in Paraquad [the advocacy group he works for] are best suited to give him advice,” according to the lawsuit. “Worth has not sought help from his colleagues for fear they could be penalized … for providing him advice.”

The Missouri lawsuit is the first to challenge a navigator-suppression law, but it may not be the last. Health care attorney Jay Angoff—the former Missouri insurance commissioner and HHS official who heads the plaintiffs’ legal team—has identified four states that bar navigators from comparing different health plans, and 10 states that penalize private citizens for helping each other find coverage. A ruling against one would invite challenges to the others.

And recent experience suggests the Missouri law is vulnerable. Tennessee’s insurance department imposed similar restrictions through “emergency rules” earlier this year, but it abandoned them this fall after health advocates filed state and federal lawsuits. In granting the Tennessee plaintiff’s request for a temporary restraining order, U.S. District Judge Todd Campbell declared that the rules likely violated both the First Amendment and the Affordable Care Act.

The Missouri case could settle those questions for good.