Selective enforcement is the ability that executors of the law (such as police officers or administrative agencies, in some cases) have to arbitrarily select choice individuals as being outside of the law. The use of enforcement discretion in an arbitrary way is referred to as selective enforcement or selective prosecution.
Historically, selective enforcement is recognized as a sign of tyranny, and an abuse of power, because it violates rule of law, allowing men to apply justice only when they choose. Aside from this being inherently unjust, it almost inevitably must lead to favoritism and extortion, with those empowered to choose being able to help their friends, take bribes, and threaten those from they desire favors.