A rule that someone calls on a friend who is crushing/stalking/etc on a person he/she is sexually attracted to, but may have a different sexual orientation.
The rule states that the friend cannot be within 30 feet of the friend's crush until his/her sexual orientation is learned.
May have first been used in the film "Camp".
Ron-John is so cute
Sharon-I declare a 30 Foot Rule! John is so straight.