I know it’s customary to allow players to “play up” into higher sections for the extra challenge. My understanding was that the opposite generally is not allowed. However, I was just looking at the crosstables of a large tournament held recently and saw players with the following ratings entered in the Under 1300 section:
Under what circumstances would it be considered kosher to admit these players into an Under 1300 section, given that they all appear to have been rated over 1300 at the time of the tournament?
The TD uses the player’s official rating (the rating published in the rating supplement for the same month as the tournament). The TD does not use a player’s unofficial rating (from last night’s tournament, for example), unless otherwise advertised (TD’s may elect to use the unofficial rating of an otherwise unrated player on occasion, but not for a rated player).
Based on the information given, you seems to refer to the U1300 section at the Chicago Open. Let’s take the #2 guy. He was rated 1285 on the May rating list, but jumped to 1536 after two tournaments in April. The May supplement was produced on the first Friday in April, since the official rating is printed on Chess Life. That means the rating used on Memorial Day weekend was 7 weeks old. The worse case scenario for ratings lag is about 8 weeks (2 months).
However, the USCF ratings calculations after the tournament will use the most updated ratings, which may in a few cases be significantly different from the ratings used for pairings and prizes.
TDs can assign players ratings higher than the one on the rating list specified for an event, but they cannot assign a lower rating than that official rating.
There are tournaments that will specify a ratings list older than the current list for that month. For example, I think the Amateur Team East uses the December list, even though the tournament is in February. One of the reasons for that is it gives people forming teams time to make sure their team rating is what they want before making travel plans.
Similarly, National Scholastic tournaments held in the first week (or so) of the month will generally use the previous month’s rating list, also largely for team formation and travel planning purposes.
another example was the K-9 unrated section of the Supernationals. I had that sectin and good number of kids actually had ratings, but not as of the cutoff for registration.