The bishop has to have some legitimate reason to dispense from the Holy Day obligation (whether that’s a feast-day or any Sunday), yet this is left to the bishop’s own discretion.
There are all sorts of legitimate reasons why he might do this. Yes, illness is one of those reasons, although people who are sick usually don’t need a dispensation (this is done more to ease their consciences than it is something necessary).
As long as the bishop himself feels that he has a good enough reason, he can grant a dispensation from any Sunday/HDO Mass. That’s his decision to make.
Apparently (or it might be better if I say “obviously”), the bishops of California all feel that they have some legitimate reason to dispense from the obligation. I don’t know what those reasons are. Each bishop decides to dispense his own diocese, so when we say “all of California” that’s more coincidental.
…
In my own country Canada there is regrettably only two Holy Days of Obligation aside from every Sunday that seem to stick out with more significance because the other Holy Days of Obligation fall into a lesser category for what ever reason I blame on the Bishops resolve to make more strict.
I have always had a great respect for the strict adherence of the American Catholic Church upholding the following list that my own country seems to be lacking in the Canadian Catholic Church.
**The following is a list of the dates of the Holy Days of Obligation in the United States for 2009, as well as the dates of moveable feasts (holy days whose dates change from year to year). Please note that only those days that have “Holy Day of Obligation” listed beneath their entries are Holy Days of Obligation; all others are moveable feasts.
• Mary, Mother of God (Thursday, January 1, 2009)
Holy Day of Obligation
• Ash Wednesday (Wednesday, February 25, 2009)
• Palm Sunday (Sunday, April 5, 2009)
• Holy Thursday (Thursday, April 9, 2009)
• Good Friday (Friday, April 10, 2009)
• Holy Saturday (Saturday, April 11, 2009)
• Easter (Sunday, April 12, 2009)
• Divine Mercy Sunday (Sunday, April 19, 2009)
• Ascension (Thursday, May 21, 2009)
Holy Day of Obligation (transferred to Sunday, May 24, 2009 in most dioceses of the United States; for more details, see When Is Ascension 2009?)
• Pentecost (Sunday, May 31, 2009)
• Trinity Sunday (Sunday, June 7, 2009)
• Corpus Christi (Thursday, June 11, 2009; transferred to Sunday, June 14, 2009)
• Assumption of Mary (Saturday, August 15, 2009)
Holy Day of Obligation (abrogated because it falls on a Saturday)
• All Saints Day (Sunday, November 1, 2009)
Holy Day of Obligation
• Christ the King (Sunday, November 22, 2009)
• First Sunday of Advent (Sunday, November 29, 2009)
Complete Advent schedule
• Immaculate Conception (Tuesday, December 8, 2009)
Holy Day of Obligation
• Christmas (Friday, December 25, 2009)
Holy Day of Obligation
Holy Days of Obligation In Canada
Christmas Day December 25th
Mary, Mother of God January 1st
I must note with sadness here in my own country that all other Holy Days of Obligation seem to fall by the wayside into a category of lesser importance and is optionally allocated to the nearest Sunday. We have the same Holy Days that the USCCB mention, but it never seems to be emphasized.**