Ex parte State Insurance Company is a United States Supreme Court case that was decided in 1873. The case involved a dispute between the State Insurance Company and the State of Mississippi. The State of Mississippi had passed a law that required all insurance companies doing business in the state to pay a tax of one percent of their gross receipts. The State Insurance Company refused to pay the tax, arguing that it was unconstitutional. The Supreme Court held that the tax was unconstitutional. The Court reasoned that the tax was a direct tax on the property of the insurance company, and that the Constitution prohibited the states from imposing direct taxes on the property of citizens of other states. The Court also held that the tax was a violation of the Due Process Clause of the Fourteenth Amendment, as it was an unreasonable and arbitrary exercise of the state's power. The Court's decision in Ex parte State Insurance Company established the principle that states cannot impose direct taxes on the property of citizens of other states. This principle has been applied in numerous cases since then, and remains an important part of constitutional law today.

In Ex Parte State Insurance Company, the Supreme Court was tasked with determining whether a state court had jurisdiction to issue an injunction against a foreign corporation. The majority of justices held that the state court did not have such authority because it would be in violation of the Constitution's Commerce Clause. Justice Field dissented from this opinion and argued that states should be allowed to exercise their power over corporations within their borders regardless of where they are incorporated or chartered. He further argued that if Congress wanted to limit states' powers in this regard, then it could do so through legislation rather than relying on constitutional interpretation by courts. Ultimately, he concluded that since no federal law prohibited such action by states, there was no reason why they should not have been able to take action against foreign corporations operating within their boundaries as long as those actions were consistent with due process requirements under both state and federal laws.