In Decker v. Northwest Environmental Defense Center, the Supreme Court upheld the EPA’s interpretation of the agency’s own regulation regarding exemption of channeled stormwater discharges from National Pollutant Discharge Elimination System permit requirements under the Clean Water Act. The Court deferred to the EPA’s interpretation under the Auer doctrine, which dictates that an administrative agency’s interpretation of its own regulation is entitled to deference unless the interpretation is plainly erroneous or inconsistent with the regulation. This Comment argues that Auer deference violates foundational separation of powers principles by allowing a governmental agency to both write and interpret the law. This power is inherently dangerous, and the ease with which it can be abused and manipulated does not bode well for the environment. Although administrative agencies possess specialized knowledge that can inform their decisionmaking, this knowledge should not give agencies a license to flaunt constitutional safeguards in the name of efficiency. The Supreme Court should have reached an opposite conclusion in Decker and should have used the case as an opportunity to overrule Auer because agencies should not be able to write and interpret the law simultaneously.