No Meat on Fridays
Many do not understand how Catholics were forbidden from eating meat on Fridays, and then in 1966 they were suddenly allowed to. To understand this, one must realise that the no meat on Fridays rule, like the celibate clergy rule, was never a doctrine but only a practice. As well, this practice was not done away with, but simply modified.
In 1966, Pope Paul IV determined that the rules for fasting and abstinence should be set by the various bishop conferences according to local circumstances. Many, but not all, conferences decided that they would allow the faithful to eat meat on Fridays if the faithful chose some other form of penance; although, abstaining from meat was still preferable.
The actual act of eating meat on Fridays was never itself a mortal sin. However, it was, and still is, a mortal sin for Catholics to wilfully disobey Church rules. At one time, it was against Church rules to eat meat on Fridays, so wilfully doing so would be a mortal sin. Now, some bishops allow the faithful to substitute another form of penance for eating meat on Fridays, so they can in good conscience eat meat on Fridays if they do some other form of penance.
Doctrines never change. Practices can.
This is just like the speed limit for the highway that connects my hometown with the big city north of us. For years it was 110km/h at day and 100km/h at night. Around thirteen or fourteen years ago, it was changed to 110km/h both day and night. Does this mean that people driving 110km/h at night twenty years ago were not speeding? Of course not. One has to follow the laws when they are in force. (I found this out the hard way. I got my first speeding ticket a few months ago in a zone that changed a few years ago from 60km/h to 50km/h. I really watch the signs now.)
Just as the rules changed so some Catholics could eat meat on Fridays, this change can be reversed. This is what Bishop R. Daniel Conlon of Steubenville did. As of April 17, 2009, Roman Catholics in the Diocese of Steubenville must abstain from meat on Fridays. You can read his letter to the faithful of his diocese concerning this here:
http://home.catholicweb.com/diosteub/index.cfm/NewsItem?id=260466
