The rule of no options is simply this: when there is no available option but to break a rule, the rule is ethically breakable.

Example: When at a train station where all bins have been removed, littering is no longer immoral.

There are many applications for this rule, imagine for instance the starving man stealing a loaf of bread for his family. Totally the right thing to do in that situation, even if it is breaking the absolute rule to not steal.

Picture dumped from here