The law governing the process for papal elections, Universi Dominici Gregis, mentions a maximum number of 120 cardinals als electors. In the media coverage of the current conclave, however, I hear that 133 cardinals are present. Am I therefore right in assuming that the 120 is not a hard limit but rather mere non-binding guidance, and that there is no mechanism to reduce the number of electors to 120 in case there are more which would otherwise meet eligibility criteria?
The rule was established by one pope, and can be disregarded by other popes.
This article was written back in March, before Francis died. It explains the situation pretty clearly.
(One interesting wrinkle discussed in that article is that the conclave itself is a matter of ecclesiastical law, subject to change by papal authority.)
Edit to add a little commentary: Reading the article closely, it seems like the “120” number is being treated as something like a target, rather than a limit. If you think about it, once the pope nominates the 120th cardinal, it won’t be very long before the number falls below 120 again due to age or death. So they generally aim to keep the number a bit above 120, so if the pope dies a few weeks or months later, natural drift will bring the number down again.
I can see the logic that an apostolic constitution is pope-made and can be overridden by a subsequent pope. But is that logic really convincing? UDC does not prohibit the pope from appointing more than 120 cardinals; it says that there shouldn’t be more than 120 voting. So the mere fact that a pope brings the number of incumbent cardinals above 120 is, arguably, not sufficient to argue that this pope also intended to suspend the limit. Sure, UDC also says that no cardinal younger than eighty can be excluded from voting; but that rule is itself in UDC, so why would it take automatic priority over the ceiling of 120 which is also in UDC?
All I know is, I’m not going to be the one to knock on the door of the Sistine Chapel and tell them they’re doing it wrong.
Using Roman numerals for math is hard.
Also keep in mind that “voting cardinals” are those under age 80 at the time the pope dies (or resigns). As the article said, 15 were about to “age out” in the next year. IIRC from another article, there are about 100 (85?) other cardinals too old to vote. A few of them are also in the conclave for various reasons, but not voting.
Seems like the 120 maximum was more a rule of thumb or guidance rather than a fixed limit.
I think one issue is: how do you pick the 120? 120 youngest cardinal-electors? Draw lots? The Dean decides as inspired by the Holy Spirit?
There were 133 voters out of 135 eligible. Two could not travel due to health.
The question should be addressed to Pope Leo. He has a doctorate in canon law, after all.
For those of us not sufficiently ordained, WTF does UDC stand for? When I try to look it up I find University of the District of Columbia or Universal Decimal Classification - neither of which seems pertinent to the discussion at hand.
Lucy
It’s Universi Dominici Gregis, the apostolic constitution (a type of statute adopted by the pope) that governs the process of the election. Like other papal documents, it’s named after and cited by its first words.
Thanks for the clarification!
However, that would make it UDG, not UDC, which is what you used in your post.
Also, (tryin’ not to be too nit-picky here) I believe that convention for initialisms is to first use full title followed by the initialism enclosed in parentheses (e.g.: Universi Dominici Gregis (UDG) ), then use the initialism in the remainder, mostly to avoid confusion such as what happened here.
The OP did use the full title (Universi Dominici Gregis) but did not use the initialism. You used UDC in your post which doesn’t even reference the title of the document in the OP. Had you used UDG I would have (probably) made the connection, but, searching on one term did not correlate with the other, hence the request for clarification.
Just sayin’. 
Lucy
[Edited to correct grammar and clarify my remarks]