I'm not saying you're wrong for thinking that, but in reality, under our system, that's not how this works.
What constitutes an unlawful detainment isn't discerned by authorities until after the detainment has already happened. Police are allowed to make judgements on the fly, often split second decisions, and it's illegal to resist them if they detain you because they decide what they believe a crime is based on their training. If they are detaining someone for allegedly committing a crime, then that person's second amendment rights have been voided.
In commuting a crime, many constitutional rights are lost regardless of if a judge decides no crime was committed later.
Therefore, there's rarely such thing as self-defense against a police officer. If someone attacks a police officer it's almost always assault regardless if the outcome of the detainment is determined to be unlawful later.
