Greenleaf v. Cook was a case heard before the United States Supreme Court in 1817. The dispute centered around whether or not an individual could be held liable for damages caused by their negligence when they had been hired to perform a service on behalf of another person, and that other person had suffered losses as a result of the negligence. In this particular case, Greenleaf had contracted with Cook to transport goods from one place to another but failed to do so properly, resulting in damage being done to those goods during transit. The court ultimately found that Greenleaf was indeed liable for any damages incurred due to his negligent performance of the contract he entered into with Cook and ordered him pay restitution accordingly. This ruling established precedent which is still used today regarding liability for services performed on behalf of others; if someone fails in their duty while performing such services then they can be held responsible for any losses suffered by those who hired them regardless of whether or not it was intentional or accidental on their part.

In Greenleaf v. Cook, Chief Justice John Marshall delivered the dissenting opinion of the court. He argued that a state law which allowed creditors to sue debtors in their own courts was unconstitutional because it violated Article IV of the Constitution, which states that citizens should be able to bring lawsuits against each other in different states without fear of being sued by local authorities. Marshall further argued that this type of law would create an unequal playing field between those who are residents and non-residents since only residents could take advantage of such laws while non-residents were left unprotected from them. Additionally, he believed this kind of legislation undermined interstate commerce as well as individual rights and liberties guaranteed by the Constitution. Finally, he concluded that if Congress had intended for such laws to exist they would have included language allowing for them when drafting Article IV or passed specific legislation authorizing them later on; however no evidence exists suggesting either occurred so therefore these kinds of laws must remain unconstitutional until otherwise stated by Congress or amended into the Constitution itself.