NASCAR Racing: Nascar rules, nascar rules, high groove

Question
what is the best explanation of the "no racing under the yellow line rule"? example, does it apply to cars that are passing lapped cars. or does it apply to cars that are racing for position. because my understanding of the rule only applies to cars that are racing for position, and if you happen to go below the line for a lapped car you don't have to give back the position and you wont get black flagged.

Answer
Hi Matt,

The no racing under the line primarily applies to cars racing for position.  For the lapped cars...it's a wait and see situation.  If the driver makes it a habit, then sure, NASCAR will black flag him.  However, if it is just one or two cars that he feels that he has to go under the line because his car dosen't handle well in the high groove of the turn, then NASCAR will more than likely, let him.
Hope I helped
Coy Jordan