Among my groups, citing a rule once is a welcome reminder... especially when an honest mistake seems like it is about to be made. Having an argument about the rules right then and there is what earns you the title Rules Lawyer. Having an argument about the rules after the game is a grey area - allowed to an extent, but unwelcome if you persist.
That attempt to debate during an unwelcome moment is the KEY in our groups.
That attempt to debate during an unwelcome moment is the KEY in our groups.