there are cases where the rules are determined by the way the situation is subjectively perceived by the person involved. their actions can later be deemed to

there are cases where the rules are determined by the way the situation is subjectively perceived by the person involved. their actions can later be deemed to be lawful or not depending on whether their perception is justified. for example - the use of lethal force has to be justifiable (this applies to everyone not just the FBI obviously), one's justification after the fact can be considered valid or not depending on circumstances.