At the Washington Post, Clay Conrad writes on the history of jury nullification in a piece entitled "History is clear: Juries were supposed to be able to overturn laws":

Jury nullification was an important part of Anglo-American law. In 1735, John Peter Zenger was charged with seditious libel for publishing newspapers criticizing the governor of New York. The law at the time left the jury to decide only whether Zenger published the papers, and let the court decide whether the papers were libelous. Defense attorney Andrew Hamilton argued that “leaving it to the judgment of the Court, whether the words are libelous or not, in effect renders juries useless (to say no worse) in many cases.”

“Gentlemen, the danger is great, in proportion to the mischief that may happen through our too great credulity. A proper confidence in a court is commendable; but as the verdict (whatever it is) will be yours, you ought to refer no part of your duty to the direction of other persons. … It is your right to do so, and there is much depending on your resolution, as well as upon your integrity.”

The transcript of Zenger’s case was widely published, and Benjamin Franklin himself commented on it. The Founding Fathers incorporated this history into the U.S. Constitution and Bill of Rights.

Conrad is the author of Jury Nullification: The Evolution of a Doctrine (Carolina Academic Press, 1999). 

The topic of nullification has enjoyed renewed interest recently. Last week, the Robert Gebelhoff asked, in another Washington Post piece, "How powerful should our juries be?"

Verdicts that ignore broken laws, such as the decision in the Reed case, are permissible under the Constitution. The Supreme Court affirmed the power of the jury in the 1895 case Sparf v. United States, arguing that a jury’s verdict cannot be questioned by any court due to the “double jeopardy” clause. Still, courts and prosecutors have long been skeptical of jury nullification. Many see it as taking away the power of sentencing discretion from judges, with whom it belongs.

Opponents of jury nullification argue that the power of juries to disregard the law is undemocratic. Laws are developed by elected representatives, they argue, not a handful of citizens gathered privately in a room. For that reason, defense attorneys are often prohibited by judges from telling jurors to make a decision contrary to the law.

But for proponents of jury powers, nullification is a right afforded to jurors that performs as a check against unjust laws. Although opponents argue that jurors have used nullification irresponsibly, they have also used the power to protect people who violated the unjust Alien and Sedition Act, the Fugitive Slave Act and prohibition laws. Advocates of nullification say that jurors should not only be able to ignore the laws when determining the verdict, but that courts should be required to inform them of their right to do so.

And Eugene Volokh wrote recently on the current push to require New Hampshire judges to inform juries of their power to nullify:

Last week, the New Hampshire House of Representatives voted 184 to 145 to pass a bill that would require courts to instruct jurors about jury nullification — the jurors’ power to refuse to convict even when they think all the elements of the crime have been proved beyond a reasonable doubt (paragraph breaks and formatting added):

In all criminal proceedings the court shall inform the jury of its right to judge the facts and the application of the law in relation to the facts in controversy.

At the request of the defendant or the defendant’s attorney, the court shall instruct the jury as follows:

If you have a reasonable doubt as to whether the state has proved any one or more of the elements of the crime charged, you must find the defendant not guilty.

However if you find that the state has proved all the elements of the offense charged beyond a reasonable doubt, you should find the
defendant guilty.

Even if you find that the state has proved all of the elements of the offense charged beyond a reasonable doubt, you may still find that based upon the facts of this case a guilty verdict will yield an unjust result, and you may find the defendant not guilty.

As the public becomes increasingly polarized politically, the number of laws an individual considers "unjust" is likely to increase, possibly explaining this renewed interest in jury nullification.