That depends. To whom do the police officers swear their loyalty? If their highest authority is The Constitution and they are trained and act as if it is, then

That depends. To whom do the police officers swear their loyalty? If their highest authority is The Constitution and they are trained and act as if it is, then maybe it's OK. But, this is a church. The church's highest authority is not The Constitution and that immediately calls into question who is the highest authority for any police officer hired and sworn by the church.