The Supreme Court unanimously ruled on Wednesday that a female police officer in St. Louis may sue for employment discrimination over a forced lateral transfer to another position in the police department.

The ruling will open the courthouse doors to more employment discrimination suits. Justice Elena Kagan, writing for six justices, said that “many cases will come out differently” under the court’s decision. But she added that “there is reason to doubt that the floodgates will open” to allow “insubstantial lawsuits.”

The case concerned Jatonya Muldrow, who worked for almost a decade in the St. Louis Police Department’s Intelligence Division, where her responsibilities included public corruption, gang violence and human trafficking. Her supervisor called her a workhorse and the “one sergeant he could count on in the division.”

In 2017, a new supervisor transferred Ms. Muldrow to another part of the department, to work as a patrol officer, replacing her with a male officer. Ms. Muldrow’s salary and rank remained the same, but her responsibilities did not.

In the Intelligence Division, she had weekends off, worked regular hours, wore plain clothes and drove an unmarked car.

The new job was more routine, had irregular hours and required her to wear a uniform and to drive a marked police car. After eight months, she was transferred back to the Intelligence Division.