Hagar v. People of the State of California was a United States Supreme Court case that addressed the issue of whether a state could impose a tax on a foreign corporation. The case was brought by the plaintiff, Hagar, who was a foreign corporation that had been assessed a tax by the State of California. Hagar argued that the tax was unconstitutional because it violated the Due Process Clause of the Fourteenth Amendment. The Supreme Court held that the tax was constitutional. The Court reasoned that the Due Process Clause did not prohibit a state from taxing a foreign corporation if the corporation had sufficient contacts with the state. The Court found that Hagar had sufficient contacts with the state, as it had been doing business in California for several years and had a substantial presence in the state. Therefore, the Court held that the tax was constitutional and could be imposed on Hagar. In conclusion, the Supreme Court held that the State of California could constitutionally impose a tax on a foreign corporation if the corporation had sufficient contacts with the state. The Court found that Hagar had sufficient contacts with the state and thus the tax was constitutional.

Justice Field delivered the dissenting opinion in Hagar v. People of the State of California, arguing that a state cannot be sued without its consent and that Congress does not have the power to authorize such suits. He argued that if Congress had intended to allow states to be sued, it would have done so explicitly in either Article III or Amendment XI of the Constitution. Furthermore, he stated that allowing individuals to sue states would create an imbalance between federal and state governments as well as undermine their sovereignty by subjecting them to judgments from which they could not appeal. Finally, Justice Field noted that there was no precedent for this type of suit against a state before this case and thus concluded it should not be allowed here either.