It means he wanted to repeal all proper law and custom before the anniversary of the Promulgation of the Code of Canon Law of 1983, which allows a practice to continue, even if it is contrary to law, if it has an unbroken use going back 30 years. Since this year is the 30th year since the 1983 Code was promulgated, it would be legally easier for the bishop to abrogate everything he wants to abrogate now, before the 30th year to the day, than after, in which case he would be legally up against the, “Well, we’ve done it this way for 30 years, this established contra legem custom, blah blah blah…”
Like if a parish had not used a tabernacle candle for the past 29 years, technically on the 30th anniversary they would be “allowed” to keep doing that as an “established custom,” even though a tabernacle choir is allowed.
All the “custom is the best interpreter of law” business has been thrown out the window, which was very clever and erudite of the bishop.
