I very recently attended a mass where the priest used the Novus Ordo, except that the priest said the entire mass “in front” of the altar with his back to the people. I do not know of any indult or other Church law that allows this. Is this under any circumstance allowed? Was this an illicit mass? This priest is very knowledgeable of liturgical law and is normally extremely careful to follow liturgical norms in detail, so I want to be absolutely certain of the facts of Church law before I approach him about this.
It is incorrect to say that the priest is saying Mass with his back to the people. In such a scenario, the priest and the people are both facing the same direction. It symbolizes the priest leading the people in the offering of the Eucharist and through their prayers the people assist. This is liturgically called ad orientem, symbolicly both the priest and the people are facing East (the direction from which Scripture says Jesus will return).
In the more common modern scenario, the priest is technically not facing the people. Both the priest and the people are facing Christ in the Eucharist.
The General Instruction for the Roman Missal does not forbid ad orientem. The GIRM is silent on which direction the priest faces except for the times that he addresses the congregation. Both Pope Benedict and Pope Francis have celebrated Mass ad orientem on certain occasions.
Every priest has the right to celebrate the Mass ad orientem.