Remember, a central idea in the Constitution is a balance of power, often called "a system of checks and balances". Much like the 2nd Amendment, the jury system is partly about preventing the government from taking too much power from the people. Deciding if a law was broken is part of it, true, but there are other aspects. For example one of the reasons for the jury is to decide if mitigating circumstances or evidence are valid enough that a violation of the letter of the law is still acceptable. A bad or unjust law is definitely a mitigating circumstance.
You frequently see people put behind bars or otherwise punished for absurd violations of absurd laws, which even the members of the jury find stupid, because they are told that their opinion of the law doesn't count, even when the law is obviously being applied in an unfair or power grabbing way. Jury nullification is a powerful tool against such abuse and absurdity.
Finally, look into the tenets of the common law system, upon which the US legal system is built. It is surprisingly enlightening, and will probably piss you off a bit at how things are currently being done (alternately, that we having fully purged it depending on your base mindset I guess :) ).
Yes. And the ultimate check on all of the other processes is the citizenry. We elect representatives of ours to write laws, we elect representatives of ours to execute laws, and we, through the jury process, judge those who are accused of breaking the laws that we (through our representatives) caused to be put into place.
In a very real way, the citizens of the jury are provided with power to prevent injustice in the application of the laws which have been put in place in our name.
You frequently see people put behind bars or otherwise punished for absurd violations of absurd laws, which even the members of the jury find stupid, because they are told that their opinion of the law doesn't count, even when the law is obviously being applied in an unfair or power grabbing way. Jury nullification is a powerful tool against such abuse and absurdity.
Finally, look into the tenets of the common law system, upon which the US legal system is built. It is surprisingly enlightening, and will probably piss you off a bit at how things are currently being done (alternately, that we having fully purged it depending on your base mindset I guess :) ).