You betcha. Just imagine how much more effective Shaquille O'Neal would be if the refs would allow him to cold-cock anyone driving to the backet.
Nope. He was being tried on a federal charge and the state law was irrelevant. The judge instructed counsel for defense not to introduce state law during the trial. That lawyer ignored the court's instruction in an attempt to prejudice the jury. He and Rosenthal's peanut gallery turned this trial into a circus and I'm surprised that he wasn't cited for contempt.
If, and it's a big if, the judge ruled that the evidence of acting as an "officer" of the City of Oakland (in what capacity, I wonder?) is "immaterial," then the issue is not whether this fact was the man's best defense, but rather that the claim is not a defense to the charges at all. In other words, "I know I got caught growing a 1000 plants, but I work for the city" might not be the best example of legal reasoning.