[canump]

Originally Posted by IRISHMAFIA

You are reading too much into this rule. Forget fair/foul territory as neither is a suggested parameter for the rules in question.

It is real simple. If, in the umpire's judgment, the runner made an attempt to advance, s/he is in jeopardy.

Knowing this took place isn't that difficult, either. As the base umpire, if at any time you feel the need to be prepared to head toward
2B, the runner probably gave you cause to think so.

Likewise even in Ontario