The IDPA rule book provides that "A competitor may compete in club matches in a division he does not have a classification in, provided he competes in the highest classification he presently holds."

 

ForScore's default behavior follows this rule, except for Classifier matches.

If you do not wish to have this behavior, mark the check box in Program Preferences on the IDPA tab.

 

For some reason, in one match I wanted to be able to selectively shut off the "register shooter in highest classification of another division".  So now I can do that for an individual shooter on his registration screen.