Except as otherwise expressly permitted by federal law, no bank holding company may acquire a Maryland bank holding company or a Maryland bank without the approval of the Commissioner. The prohibition in subsection (a) of this section shall not apply where the acquisition is made: Solely for the purpose of facilitating an acquisition otherwise permitted under this subtitle; In a transaction arranged by the Commissioner or another bank supervisory agency to prevent the insolvency or closing of the acquired bank; or In a transaction in which a bank forms its own bank holding company, if the ownership rights of the former bank shareholders are substantially similar to those of the shareholders of the new holding company. In a transaction for which the Commissioner’s approval is not required under this section, the parties shall give written notice to the Commissioner at least 15 days before the effective date of the acquisition.