The Securities Exchange Act of 1934 (as amended by the Dodd Frank Act), 15 U.S. Code §78u-6:
Securities whistleblower incentives and protection…(h) Protection of whistleblowers (1) Prohibition against retaliation (A) In general No employer may discharge, demote, suspend, threaten, harass, directly or indirectly, or in any other manner discriminate against, a whistleblower in the terms and conditions of employment because of any lawful act done by the whistleblower— (i) in providing information to the Commission in accordance with this section; (ii) in initiating, testifying in, or assisting in any investigation or judicial or administrative action of the Commission based upon or related to such information; or (iii) in making disclosures that are required or protected under the Sarbanes-Oxley Act of 2002 (15 U.S.C. 7201 et seq.), this chapter, including section 78j–1(m) of this title, section 1513(e) of title 18, and any other law, rule, or regulation subject to the jurisdiction of the Commission. (B) Enforcement (i) Cause of action An individual who alleges discharge or other discrimination in violation of subparagraph (A) may bring an action under this subsection in the appropriate district court of the United States for the relief provided in subparagraph (C).
See SEC interpretation, as the law pertains to employees who do not report to the Commission, at https://www.sec.gov/rules/interp/2015/34-75592.pdf.
In addition, the anti-retaliation provisions under the Sarbanes Oxley Act of 2002 expressly protect employees who report violations internally to supervisors or other company representatives. 18 U.S.C. §1514A(a)(1)(C) (protecting those who report to “a person with supervisory authority over the employee (or such other person working for the employer who has the authority to investigate, discover, or terminate misconduct)”
18 U.S. Code §1514A – Civil action to protect against retaliation in fraud cases (a)Whistleblower Protection for Employees of Publicly Traded Companies.—No company with a class of securities registered under section 12 of the Securities Exchange Act of 1934 (15 U.S.C. 78l), or that is required to file reports under section 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78o(d)) including any subsidiary or affiliate whose financial information is included in the consolidated financial statements of such company, or nationally recognized statistical rating organization (as defined in section 3(a) of the Securities Exchange Act of 1934 (15 U.S.C. 78c),[1] or any officer, employee, contractor, subcontractor, or agent of such company or nationally recognized statistical rating organization, may discharge, demote, suspend, threaten, harass, or in any other manner discriminate against an employee in the terms and conditions of employment because of any lawful act done by the employee—(1) to provide information, cause information to be provided, or otherwise assist in an investigation regarding any conduct which the employee reasonably believes constitutes a violation of section 1341, 1343, 1344, or 1348, any rule or regulation of the Securities and Exchange Commission, or any provision of Federal law relating to fraud against shareholders, when the information or assistance is provided to or the investigation is conducted by—(A) a Federal regulatory or law enforcement agency; (B) any Member of Congress or any committee of Congress; or (C) a person with supervisory authority over the employee (or such other person working for the employer who has the authority to investigate, discover, or terminate misconduct)….