This document changes a rule interpreting the anti-retaliation provision of the Occupational Safety and Health Act of 1970, 29 U.S.C. 660(c). That provision prohibits adverse action, such as a discharge, against employees because they have engaged in protected activity, such as complaining about unsafe or unhealthful working conditions. The revised interpretive rule clarifies the causal connection between the protected activity and the adverse action. 29 CFR 1977.6. In order to prove a violation of this provision the Secretary of Labor must show that but for the employee’s protected activity he or she would not have suffered an adverse action. This interpretation is based on Supreme Court precedents interpreting similar language dealing with causation under the anti-retaliation provision of title VII of the Civil Rights Act of 1964 and the Age Discrimination in Employment Act, as well as other precedents. See University of Texas Southwestern Medical Center v. Nassar, 570 U.S. 338 (2013).