A more thorough explanation:

Klaxon doctrine is a legal principle that applies to conflict of laws cases. It states that when a federal court has diversity jurisdiction, meaning the case involves parties from different states, the court must apply the choice-of-law rules of the state where the court is located.

For example, if a case is being heard in a federal court in California and involves parties from California and New York, the court must apply California's choice-of-law rules to determine which state's laws apply to the case.

The Klaxon doctrine was established in the case of Klaxon Co. v. Stentor Elec. Mfg. Co. by the Supreme Court in 1941. This decision extended the rule of Erie v. Tompkins to choice-of-law issues.

The Erie doctrine, which was established in 1938, is another legal principle that applies to diversity jurisdiction cases. It states that federal courts must apply the substantive law of the state where the court is located in cases that do not involve a federal question.

For example, if a case is being heard in a federal court in Texas and involves a dispute between two Texas residents, the court must apply Texas law to the case.

Overall, the Klaxon doctrine and the Erie doctrine are important principles that help ensure consistency and fairness in the application of laws in federal courts.