JUSTICE BRENNAN delivered the opinion of the Court.

[1] Section 685 of the California Insurance Code imposes a retaliatory tax on out-of-state insurers doing business in California, when the insurer’s State of incorporation imposes higher taxes on California insurers doing business in that State than California would otherwise impose on that State’s insurers doing business in California.

[2] [The issue in this case is whether the retaliatory tax violates negative implications of the Commerce Clause].

**

[3] In a long line of cases stretching back to the early days of the Republic . . . this Court has recognized that the Commerce Clause contains an implied limitation on the power of the States to interfere with or impose burdens on interstate commerce. Even in the absence of congressional action, the courts may decide whether state regulations challenged under the Commerce Clause impermissibly burden interstate commerce.

[4] Our decisions do not, however, limit the authority of Congress to regulate commerce among the several States as it sees fit. In the exercise of this plenary authority, Congress may “confe[r] upon the States an ability to restrict the flow of interstate commerce that they would not otherwise enjoy.” If Congress ordains that the States may freely regulate an aspect of interstate commerce, any action taken by a State within the scope of the congressional authorization is rendered invulnerable to Commerce Clause challenge.

[5] Congress removed all Commerce Clause limitations on the authority of the States to regulate and tax the business of insurance when it passed the McCarran-Ferguson Act, as this Court acknowledged in State Board of Insurance v. Todd Shipyards Corp., 370 U. S. 451, 452 (1962). Nevertheless, Western & Southern, joined by the Solicitor General as amicus curiae, argues that the McCarran-Ferguson Act does not permit “anti-competitive state taxation that discriminates against out-of-state insurers.” We find no such limitation in the language or history of the Act.

[6] Section 1 of the Act, contains a declaration of policy:

[7] “Congress declares that the continued regulation and taxation by the several States of the business of insurance is in the public interest, and that silence on the part of the Congress shall not be construed to impose any barrier to the regulation or taxation of such business by the several States.”

[8] Section 2 (a) declares: “The business of insurance . . . shall be subject to the laws of the several States which relate to the regulation or taxation of such business.” The unequivocal language of the Act suggests no exceptions.

**

[9] We must therefore reject Western & Southern’s Commerce Clause challenge to the California retaliatory tax: the McCarran-Ferguson Act removes entirely any Commerce Clause restriction upon California’s power to tax the insurance business.