About 1,000 or more instructors at the University of Minnesota would not be eligible to join the same union as tenured professors, an appeals court has ruled.

The ruling, announced Tuesday, is a setback for activists who have been trying to organize a faculty union on the Twin Cities campus since January 2016.

The Minnesota Court of Appeals sided with the university in the dispute over how many people may be included in a potential bargaining unit. The court ruled Tuesday that, under state law, tenure-track faculty cannot be grouped with other categories of instructors, such as lecturers and teaching specialists, in the same union.

The court reversed a 2016 ruling by the state’s Board of Mediation Services, which had sided with the union organizers.

Tuesday’s decision excludes most of the university’s part-time or contingent faculty members from the proposed bargaining unit, organizers say. It would permit about 1,950 other faculty members, most of them tenure-track professors, to vote on whether to form a union, according to the U.

Anna Kurhajec, a part-time American Studies instructor, said she was disappointed by the ruling.

“It is a blow,” she said, noting that it excludes the very faculty members who most need a union — those with no tenure or job security. Kurhajec, who is one of the union organizers, said the group will meet later this week to consider an appeal.

The group, known as Minnesota Academics United, has been working for more than two years to organize the faculty at the U as part of a nationwide campaign by the Service Employees International Union.

The university released a brief statement, saying it was pleased with the court’s decision.