A New Jersey university's plan to sell its music college to another institution is now facing a legal challenge.

Supporters of Westminster Choir College sued Rider University on Tuesday. They claim any sale that would close the music school or move it from its 23-acre (9-hectare) campus in Princeton is illegal and would violate a 1991 merger agreement between the two institutions.

Rider announced in March that it had hired an outside firm to seek a buyer for its music school and campus. They also may consider selling the school to a buyer who would move it to its own campus.

The decision came as Rider seeks to boost enrollment and faces a potential $13 million shortfall by 2019.

A Rider spokeswoman says the university disagrees with the lawsuit's contentions.