The Church’s Code of Canon Law states: “Marriage … is to be celebrated in a parish church. By permission of the local ordinary or of the parish priest, it may be celebrated in another church or oratory. The local ordinary can allow a marriage to be celebrated in another suitable place” (Canon 1118).
The comment on the law observes “suitable places” may include churches of other denominations, halls or private homes. Might permission be extended to outdoor ceremonies? If the bishop of the place agrees, a couple could certainly exchange their vows outdoors, and many Catholics can undoubtedly recall a time, not terribly long ago, when outdoor ceremonies were not altogether uncommon.
The issue is preserving the sacred character of the event. A wedding is not simply a party, nor is a church simply a building. In the early days of our faith a church building was known as “the house of the church,” to describe its function as the gathering place of God’s People. The Catechism of the Catholic Church quotes John Chrysostom to describe the unique role of the church building: “You cannot pray at home as at church, where there is a great multitude … and something more … the accord of souls, the bond of charity” (No. 2179).