ANN ARBOR, Mich. - A gun owners' group and an Ann Arbor parent have sued the Michigan city's school district over a new policy to keep guns out of schools, except for those carried by law enforcement officers.

The Ann Arbor News reports that Michigan Gun Owners and parent Ulysses Wong filed the lawsuit Monday against the Ann Arbor Public Schools and Superintendent Janice Swift. It alleges the policy enacted this month violate state law and the constitution.

Under the policy, a weapon in a school constitutes an emergency; if anyone other than a law enforcement officer carries a gun into an Ann Arbor school, administrators will ask the person to leave and call the police, reports CBS Detroit.

Ann Arbor school officials explored a weapons-free policy amid debate about whether it's appropriate to openly carry firearms in schools.

The debate came after Joshua Wade, who has a concealed pistol license, brought a gun into Pioneer High School during a choir concert and a disruption ensued.

School officials had anticipated a lawsuit stemming from the new gun policy, and said they were not worried.

"I'm pleased that we have approved a policy that will protect students and if tested in court we will be able to defend successfully," said School Board Trustee Andy Thomas, according to the station.