Niswanger v. Saunders was a case heard by the US Supreme Court in 1863 that dealt with the issue of whether or not an individual could be held liable for damages caused to another person's property due to negligence. The plaintiff, Niswanger, had sued Saunders after his cattle destroyed some of her crops and she sought compensation for the damage done. The court ruled in favor of Niswanger and found that individuals can indeed be held liable for damages caused by their own negligence even if they did not intend to cause any harm. This ruling established a precedent that has been applied ever since, holding people accountable when their actions lead to injury or destruction of someone else's property regardless of intent.

In Niswanger v. Saunders, the Supreme Court was asked to decide whether a state court could enforce an agreement made in another state. The majority of justices held that it could not because such agreements were considered void under the Full Faith and Credit Clause of the Constitution. However, Justice Grier dissented from this opinion on two grounds: firstly, he argued that there was no evidence that Congress had intended for states to be bound by contracts made in other states; secondly, he maintained that if Congress had intended for such agreements to be binding then they should have been enforced as long as they did not violate public policy or local laws within each respective state. He concluded his dissent by stating that "the power which can make a contract valid cannot unmake it."