If you want to get the judge to excuse you from jury duty, just let her/him know that you’ve read a book or two (maybe Lysander Spooner’s Essay on Trial by Jury) about jury nullification. Maybe bring one with you. I think the judge will be happy to send you on your way.
The hard question is, what if you actually want to serve on the jury, in hopes of nullifying a bad law? They get pretty mad if they think you’ve lied to them, but how do you get on a jury without hiding the truth?
And what if you end up on a jury? Will it be easy to stick to your guns, if you are the only juror voting for acquittal?