Lanusse v. Barker was a case heard by the United States Supreme Court in 1818 that dealt with the issue of whether or not an individual could be held liable for debts incurred before they were married to their spouse. The plaintiff, Lanusse, argued that he should not be responsible for his wife's pre-marital debt because it had been contracted prior to their marriage and thus did not become his responsibility upon marrying her. The defendant, Barker, argued that since Lanusse had assumed control over all of his wife's property after marriage - including any existing debts - he should therefore also assume liability for them as well. Ultimately, the court sided with Lanusse and ruled that individuals are only responsible for debts incurred during their own lifetime and cannot be held liable for those taken on by another person prior to entering into a marital relationship.

In Lanusse v. Barker, the Supreme Court was asked to decide whether a state court had jurisdiction over a case involving two citizens of different states. The majority opinion held that the state court did not have jurisdiction because it would be in violation of Article III, Section 2 of the Constitution which grants exclusive federal judicial power over cases between citizens from different states. Justice Story dissented and argued that while there may be some constitutional issues with allowing state courts to hear such cases, those concerns should not prevent them from doing so as long as they are acting within their own authority granted by their respective legislatures. He further argued that if Congress wanted to limit or restrict this type of action by state courts then they should pass legislation explicitly prohibiting it instead of relying on an interpretation of the Constitution which is open for debate and could lead to conflicting decisions among various jurisdictions.