This is the first Supreme Court case which recognized and established the principle that in a jury trial the jury has the right and duty to judge the law as well as the facts in a case, which was later to be undermined by Sparf v. U.S. The key quote is:
... on questions of fact, it is the province of the jury, on questions of law, it is the province of the court to decide. But it must be observed that by the same law, which recognizes this reasonable distribution of jurisdiction, you have nevertheless a right to take upon yourselves to judge of both, and to determine the law as well as the fact in controversy. On this, and on every other occasion, however, we have no doubt, you will pay that respect, which is due to the opinion of the court: For, as on the one hand, it is presumed, that juries are the best judges of facts; it is, on the other hand, presumbable, that the court are the best judges of the law. But still both objects are lawfully, within your power of decision. Chief Justice John Jay.
1. Sparf & Hansen v. United States, 156 U.S. 51, 64 (1895).