I recently had the following problem: In my own diocese (Cologne, Germany) the day of Corpus Christi is a legal and ecclesiastical holiday on the respective Thursday. However, I’m often in the Netherlands, where Corpus Christi is celebrated on the following Sunday. This time I travelled back on Saturday, so that I missed Corpus Christi in both dioceses. Now I figured that I had to go by the rules of the diocese in which I am, not that which I come from. I still went to Mass on Thursday (which was just a normal evening mass, of course).
Now two questions. 1.) In my interpretation I was not obliged to go to Mass on the Thursday of Corpus Christi, or was I? 2.) In my interpretation, if I happen to be in some diocese on a day that is a strict holiday in that diocese, then I would be obliged to go even if it weren’t one in my own diocese. Is that correct?
Thank you and God bless you.
Code of Canon Law:
Can. 12 §3. Laws established for a particular territory bind those for whom they were issued as well as those who have a domicile or quasi-domicile there and who at the same time are actually residing there…
What this canon means is that we are obligated to follow the rules of the diocese in which we actually live (domicile) or are staying in for a minimum of 3 months (quasi-domicile). So as long as you are in the Netherlands for less than 3 months then you would follow the laws of your home diocese. So you were correct to attend Mass on Thursday since that is the law of your home diocese. It does not matter that the Mass was not a Corpus Christi Mass, the obligation is simply to attend Mass.
If you were in the Netherlands, for less than 3 months, and there was a holy day of obligation that was not one in your home diocese you would not be obligated to attend. Obviously you still could if you wanted to, but there is no canonical obligation to do so.