Reactance is the psychological term defining the human tendency of reacting negatively towards situations perceived to be limiting personal freedom of choice. Wikipedia defines it as such:
Reactance is a motivational reaction to offers, persons, rules, or regulations that threaten or eliminate specific behavioral freedoms. Reactance occurs when a person feels that someone or something is taking away his or her choices or limiting the range of alternatives.
It’s a very important concept to grasp for choice architecture because it’s the source of many backfiring risks.