Is there a word for someone who enforces rules using a double standard because of some bias?

An example would be an officer choosing to give person A a speeding ticket and choosing to not give person B a speeding ticket, even if both persons were speeding in identical situations on different instances. Person A might be a different race or gender to person B, for instance, or the officer might have had some other bias.

Another would be say, a park has a sign up that says "no pets on grass" which goes ignored regularly by many people. A citizen might choose to oppose a particular person for breaking said rule while choosing to ignore it for others. The underlying reason is that the citizen simply doesn’t like the person they are confronting because of some bias, and projecting that through "being right" about some rule.