Jury nullification is the process where a jury either finds that a law being applied in the trial is unlawful or that the evidence, or lack thereof, doesn’t support the charge, thus nullifying the law, the evidence and/or both! The practice of nullification by a jury goes back hundreds of years and was a way to ensure that citizens didn’t suffer directly under tyrannical rule of the state or by a biased judge, but rather sought to rely on a jury of “peers” to either acquit or convict an individual.
Here’s a few laws found in the Magna Carta, the U.S. Constitution, Supreme Court rulings, and quotes from the past on a quick search:
Article 20 of the Magna Carta reads:
For a trivial offence, a free man shall be fined only in proportion to the degree of his offence, and for a serious offence correspondingly, but not so heavily as to deprive him of his livelihood. In the same way, a merchant shall be spared his merchandise, and a husbandman the implements of his husbandry, if they fall upon the mercy of a royal court. None of these fines shall be imposed except by the assessment on oath of reputable men of the neighbourhood.
Article 39 of the Magna Carta reads:
No freeman shall be arrested or imprisoned or deprived of his freehold or outlawed or banished or in any way ruined, nor will we take or order action against him, except by the lawful judgment of his equals and according to the law of the land.
5th Amendment of the U.S. Constitution reads:
No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.
7th Amendment of the U.S. Constitution reads:
In Suits at common law, where the value in controversy shall exceed twenty dollars, the right of trial by jury shall be preserved, and no fact tried by a jury, shall be otherwise re-examined in any Court of the United States, than according to the rules of the common law.
Article III, Section 2, Paragraph  of the U.S. Constitution reads:
The trial of all Crimes, except in Cases of Impeachment, shall be by Jury; and such Trial shall be held in the State, where the said Crimes shall have been committed; but when not committed within any State, the Trial shall be at such Place or Places as the Congress may by Law have directed.
Pennsylvania’s Constitution (my home state) in Article I., Section 7 reads:
The printing press shall be free to every person who may undertake to examine the proceedings of the Legislature or any branch of government, and no law shall ever by made to restrain the right thereof. The free communication of thoughts and opinions is one of the invaluable rights of man, and every citizen may freely speak, write and print on any subject, being responsible for the abuse of that liberty. No conviction shall be had in any prosecution for the publication of papers relating to the official conduct of officers or men in public capacity, or to any other matter proper for public investigation or information, where the fact that such publication was not maliciously or negligently made shall be established to the satisfaction of the jury; and in all indictments for libels the jury shall have the right to determine the law and the facts, under the direction of the court, as in other cases.
In Georgia v. Brailsford (1794), Chief Justice John Jay wrote:
It is presumed, that juries are the best judges of facts; it is, on the other hand, presumed that courts are the best judges of law. But still both objects are within your power of decision… you [juries] have a right to take it upon yourselves to judge both, and to determine the law as well as the fact in controversy.
In Morissette v. United States (1952), the Supreme Court wrote:
Had the jury convicted on proper instructions it would be the end of the matter. But juries are not bound by what seems inescapable logic to judges….They might have refused to brand Morissette as a thief. Had they done so, that too would have been the end of the matter
In U.S. v. Moylan (1969), the 4th circuit affirmed the power of the jury:
We recognize, as appellants urge, the undisputed power of the jury to acquit, even if its verdict is contrary to the law as given by the judge, and contrary to the evidence. This is a power that must exist as long as we adhere to the general verdict in criminal cases, for the courts cannot search the minds of the jurors to find the basis upon which they judge. If the jury feels that the law under which the defendant is accused, is unjust, or that exigent circumstances justified the actions of the accused, or for any reason which appeals to their logic or passion, the jury has the power to acquit, and the courts must abide by that decision.
In U.S. v Dougherty (1972), the Court wrote:
The pages of history shine on instances of the jury’s exercise of its prerogative to disregard instructions of the judge; for example, acquittals under the fugitive slave law.
John Locke wrote in his second Treatise of Government:
Yet the legislative being only a fiduciary power to act for certain ends, there remains still in the people a supreme power to remove or alter the legislative, when they find the legislative act contrary to the trust reposed in them….And thus the community perpetually retains a supreme power of saving themselves from the attempts and designs of any body, even of their legislators, whenever they shall be so foolish or so wicked as to lay and carry on designs against the liberties and properties of the subject.
John Adams, when defending John Hancock in 1771, wrote:
It’s not only ….(the juror’s) right, but his duty, in that case, to find the verdict according to his own best understanding, judgement, and conscience, though in direct opposition to the direction of the court.
Thomas Jefferson wrote in the Notes on Virginia in 1782:
…..it is usual for the jurors to decide the fact, and to refer the law arising on it to the decision of the judges. But this division of the subject lies with their discretion only. And if the question relate to any point of public liberty, or if it be one of those in which the judges may be suspected of bias, the jury undertake to decide both law and fact.
Thomas Jefferson wrote in a letter to Thomas Paine in 1789:
I consider trial by jury as the only anchor yet imagined by man by which a government can be held to the principles of its constitution.
Supreme Court Justice Samuel Chase wrote in 1796:
The jury has the right to determine both the law and the facts.
Alexander Hamilton in 1804 wrote:
Jurors should acquit, even against the judge’s instruction…if exercising their judgement with discretion and honesty they have a clear conviction that the charge of the court is wrong.