regarding underpayment of tax or any conduct which the employee reasonably believes constitutes a violation of the internal revenue laws or any provision of Federal law relating to tax fraud, when the information or assistance is provided to the Internal Revenue Service, the Secretary of Treasury, the Treasury Inspector General for Tax Administration, the Comptroller General of the United States, the Department of Justice, the United States Congress, a person with supervisory authority over the employee, or any other person working for the employer who has the authority to investigate, discover, or terminate misconduct, or (B) to testify, participate in, or otherwise assist in any administrative or judicial action taken by the Internal Revenue Service relating to an alleged underpayment of tax or any violation of the internal revenue laws or any provision of Federal law relating to tax fraud. (2) Enforcement action (A) In general A person who alleges discharge or other reprisal by any person in violation of paragraph (1) may seek relief under paragraph (3) by— (i) filing a complaint with the Secretary of Labor, or (ii) if the Secretary of Labor has not issued a final decision within 180 days of the filing of the complaint and there is no showing that such delay is due to the bad faith of the claimant, bringing an action at law or equity for de novo review in the appropriate district court of the United States, which shall have jurisdiction over such an action without regard to the amount in controversy. (B) Procedure (i) In general An action under subparagraph (A)(i) shall be governed under the rules and procedures set forth in section 42121(b) of title 49, United States Code. (ii) Exception Notification made under section 42121(b)(1) of title 49, United States Code, shall be made to the person named in the complaint and to the employer. (iii) Burdens of proof An action brought under subparagraph (A)(ii) shall be governed by the legal burdens of proof set forth in section 42121(b) of title 49, United States