On Tuesday the U.S. Supreme Court held that a public employee could sue his employer for retaliation where the employer demoted him for engaging in constitutionally-protected political activity, even though the employer was factually mistaken about the employee’s actual involvement in the activity.

In Heffernan v. City of Paterson, a police detective, Heffernan, was supervised by an individual appointed by the incumbent mayor as well as the chief of police, who likewise was appointed by the mayor. During the mayoral campaign, Heffernan’s bedridden mother asked Heffernan to pick up and deliver to her a campaign yard sign supporting the mayor’s opponent. Heffernan’s fellow police officers viewed him holding the sign and speaking to staff at a distribution point for the opposing candidate, and word quickly spread among the force.

Heffernan was demoted the very next day for his perceived “overt involvement” in the opponent’s campaign. In fact, Heffernan was not involved in the campaign, and thus the City’s action was based on a factual mistake. The question before the Court was whether Heffernan, who was punished for constitutionally-protected political activity but did not actually engage in that activity, could maintain a claim alleging a violation of the First Amendment and 42 U.S.C. § 1983.

Reversing the Third Circuit Court of Appeals, the Court held that Heffernan could maintain his claim. The Court first recognized well-established precedent that a public employer may not discharge or demote an employee for supporting a particular political candidate (with very limited exceptions not applicable here). The Court then focused on the motive for and effect of the City’s actions, which it found were the same whether or not Heffernan had actually engaged in any political activity. As to effect, the City’s demotion of Heffernan served to deter other employees from engaging in constitutionally-protected activity. “The upshot is that a discharge or demotion based upon an employer’s belief that the employee has engaged in protected activity can cause the same kind, and degree, of constitutional harm whether that belief does or does not rest upon a factual mistake,” concluded Justice Stephen Breyer, writing for the 6-2 majority.

Thus, the Court held that when a public employer takes an adverse action against a public employee for the purpose of preventing the employee from engaging in protected political activity, the employee is entitled to challenge the action, even if the employer is mistaken about the employee’s behavior.

In this election season, this case serves as an effective reminder to public employers to be mindful of the limitations on taking action against public employees for their political or other free-speech activity—whether real, or simply perceived.