I’m not so sure about that anymore. Jimmy Akin argues the obligation of penance is not under pain of mortal sin during non Lenten Fridays:
(His words are in blue, the US bishops words are italicized)
3. Among the works of voluntary self-denial and personal penance which we especially commend to our people for the future observance of Friday,* even though we hereby terminate the traditional law of abstinence as binding under pain of sin, *as the sole prescribed means of observing Friday, we give first place to abstinence from flesh meat. We do so in the hope that the Catholic community will ordinarily continue to abstain from meat by free choice as formerly we did in obedience to Church law. Our expectation is based on the following considerations
The big legal change comes in norm #3, where the bishops state that “we hereby terminate the traditional law of abstinence as binding under pain of sin, as the sole prescribed means of observing Friday.” So the obligation to abstain from meat is terminated. The question becomes: What obligation, if any, have the bishops put in its place?
To find out what other obligation there may be, one must look at the surrounding text of the norms. When one does this, one discovers several things.
The first, per norm #3, is that the bishops “especially commend to our people for the future observance of Friday . . . we give first place to abstinence from flesh meat.” This is an exhortation and as such does not establish a legal obligation. So abstinence continued to be a recommended practice for the observance of Friday, but not a legally binding one.
The next thing, per norm #1, is that Friday continues to be a day of penance. The norm clarifies the sense in which this is to be understood by explaining that it is “a time when those who seek perfection will be mindful of their personal sins and the sins of mankind which they are called upon to help expiate in union with Christ Crucified.” This qualification strongly suggests that, though Friday is a day of penance, it is not one on which all of the faithful are legally bound or bound under pain of sin to do penance. Instead, “those who seek perfection” will do penance on the day. If the bishops intended all to be bound to do penance on Friday, they would not have used such restrictive language.
This interpretation is confirmed by norm #2, which states that “Friday should be in each week something of what Lent is in the entire year. For this reason we urge all to prepare for that weekly Easter that comes with each Sunday by freely making of every Friday a day of self-denial and mortification in prayerful remembrance of the passion of Jesus Christ.” Again, the language of exhortation is used (“we urge”) rather than the language of mandate. Thus no obligation is created. If the bishops intended to create an obligation then they would have used other language, such as “all are required to prepare for that weekly Easter.”
The norms–the part of the document that would create a legal obligation if there was one–thus fails to do so. As a result, there is no obligation in the United States to practice penance on Friday, but Friday remains a day of penance which the bishops have urged all to do penance and, in particular, recommended the continued practice of abstience.
Reading the remainder of the document confirms the interpretation outlined above. As a compromise document and a controversial one, the stress that is placed on the recommendation to continue to do penance and to abstain is great, and with an inattentive reading the strength of the recommendation might lead one to think that there is an obligation to do penance on Friday. But a careful reading of the text shows that the language being used in the text never strays from the language of exhortation to the language of legal mandate.
There also is a dog that didn’t bark in this text.
The bishops were so concerned to avoid the impression that they were gutting the practice of penance that if they were creating an alternative obligation then they could not have failed to underscore this point. It would have been the most crushing rejoinder to their potential critics if they had said something like, “Though we have terminated the obligation to abstain, the faithful are nevertheless bound to perform a penance of their choice on Fridays and thus the Catholic practice of Friday penance remains in place even though the form the penance takes is now left to the determination of the individual.” The fact that the bishops nowhere say this or anything like it strongly indicates that it was not the bishops’ intent to create an alternative obligation. Calling attention to the alternative obligation by frankly stating it would have utterly invalidated the criticism the bishops were most concerned to avoid.
But the fact that the bishops nowhere state an alternative obligation indicates that one does not exist. Legal obligations do not exist that are not legislated.
Thus we conclude that the American bishops have exercised their competence, later acknowledged by canon 1253 of the 1983 Code of Canon Law, to determine more particularly the manner of abstinence by restricting it to a few days a year (Ash Wednesday, the Fridays of Lent, and Good Friday–the last being part of Triduum rather than Lent) and by recommending the continued practice of abstinence on other Fridays. Rome confirmed this document, and thus it is the law for Latin Catholics in the United States.