Alice is annoyed with Bob and threatens him with punishment not only if he does a particular action but even if he thinks about doing it In RL it's a step-up for emphasis from the threat 'If you ever do...'. This trope occurs in either of the following situations:
1) Alice believes that thinking of an action is as bad as the action
2) Alice can actually enforce this through mind reading, hypnotism etcetra
One particular bit of fridge logic over this trope is that you have to actually think of doing an activity before adding the not qualifier, so anyone trying this would be hamstrung. Think of not thinking of Pink Elephants.