15 U.S. Code § 6715. Certain State affiliation laws preempted for insurance companies and affiliates

Except as provided in section 6701(c)(2) of this title, no State may, by law, regulation, order, interpretation, or otherwise—
prevent or significantly interfere with the ability of any insurer, or any affiliate of an insurer (whether such affiliate is organized as a stock company, mutual holding company, or otherwise), to become a financial holding company or to acquire control of a depository institution;
limit the amount of an insurer’s assets that may be invested in the voting securities of a depository institution (or any company which controls such institution), except that the laws of an insurer’s State of domicile may limit the amount of such investment to an amount that is not less than 5 percent of the insurer’s admitted assets; or
prevent, significantly interfere with, or have the authority to review, approve, or disapprove a plan of reorganization by which an insurer proposes to reorganize from mutual form to become a stock insurer (whether as a direct or indirect subsidiary of a mutual holding company or otherwise) unless such State is the State of domicile of the insurer.