Checks and balances considered useful. I always want the option to exist, even though people won't need it in most cases.

And also, every case adds to the case history; it doesn't take many cases to create a pattern. So no, the results don't only apply to that one case. And even if they do, a single instance of well-applied nullification might not mean much to the general public, but it means the world to the defendant.

>> We already have a system to make sure laws remain appropriate: it is called an elected legislature.

The legislature does no such thing. Theoretically, representatives do their job by pandering to constituent majorities.

http://en.wikipedia.org/wiki/Tyranny_of_the_majority

Indeed, selective application of the law is a tyranny in itself, and the public gets awfully bent out of shape when police officers try it.