Canon 670

1. For a just cause Catholics can attend the liturgical worship

of other Christians and take part in the same, observing those

things which, by reason of the degree of communion with the Catholic Church, are established by the eparchial bishop or by a superior authority. 2. If non-Catholic Christians lack a place in

which divine worship can be celebrated with dignity, the eparchial bishop can grant the use of a Catholic building or cemetery

or church according to the norm of particular law of his own

Church sui iuris.