A bishop's authority

Question from Stephen on 2/5/2008:  
Dear Father, please could you tell me if this is the correct application of canon law. An archbishop has excommunicated an alleged visionary as well as those who visit the place of apparitions-but he has also said that any catholic-clergy or laity from anywhere in the world will also be excommunicated if they visit the place. It was my understanding that he only has authority over those in his own diocese, and as many bishops from around the world visit this place, does that mean they will incur automatic excommunication? Thanks in advance Stephen
Answer by Rev. Mark J. Gantley, JCL on 2/20/2008: 
Generally speaking a diocesan bishop can exercise authority over his own subjects as well as travelers in the territory of his diocese.

There are limits in terms of bishops in his territory (e.g., penal cases involving bishops can only be handled by the Apostolic See).

It is hard to give a more specific answer without more information or a more specific question. Often, to give a complete answer, I might need to see the documents involved (e.g., decrees, norms promulgated by the bishop).

There is also a different between having an excommunication imposed and one incurred by the law itself (latae sententiae, commonly called "automatic," although it is a bit simplistic to put it that way). You first refer to an bishop imposing excommunication and then you refer to automatic excommunications.