From Justice Kagan's dissent on page 82:
> This Court has long understood Chevron deference to reflect what Congress would want, and so to be rooted in a presumption of legislative intent. Congress knows that it does not—in fact cannot—write perfectly complete regulatory statutes...
> It knows that those statutes will inevitably contain ambiguities that some other actor will have to resolve, and gaps that some other actor will have to fill. And it would usually prefer that actor to be the responsible agency, not a court...
> Put all that together and deference to the agency is the almost obvious choice, based on an implicit congressional delegation of interpretive authority. We defer, the Court has explained, “because of a presumption that Congress” would have “desired the agency (rather than the courts)” to exercise “whatever degree of discretion” the statute allows. Smiley v. Citibank (South Dakota), N. A., 517
U. S. 735, 740–741 (1996).
> Today, the Court flips the script: It is now “the courts (rather than the agency)” that will wield power when Congress has left an area of interpretive discretion. A rule of judicial humility gives way to a rule of judicial hubris. In recent years, this Court has too often taken for itself decision-making authority Congress assigned to agencies. The Court has substituted its own judgment on workplace health for that of the Occupational Safety and Health Administration; its own judgment on climate change for that of the Environmental Protection Agency; and its own judgment on student loans for that of the Department of Education.
> This Court has long understood Chevron deference to reflect what Congress would want, and so to be rooted in a presumption of legislative intent. Congress knows that it does not—in fact cannot—write perfectly complete regulatory statutes...
> It knows that those statutes will inevitably contain ambiguities that some other actor will have to resolve, and gaps that some other actor will have to fill. And it would usually prefer that actor to be the responsible agency, not a court...
> Put all that together and deference to the agency is the almost obvious choice, based on an implicit congressional delegation of interpretive authority. We defer, the Court has explained, “because of a presumption that Congress” would have “desired the agency (rather than the courts)” to exercise “whatever degree of discretion” the statute allows. Smiley v. Citibank (South Dakota), N. A., 517 U. S. 735, 740–741 (1996).
> Today, the Court flips the script: It is now “the courts (rather than the agency)” that will wield power when Congress has left an area of interpretive discretion. A rule of judicial humility gives way to a rule of judicial hubris. In recent years, this Court has too often taken for itself decision-making authority Congress assigned to agencies. The Court has substituted its own judgment on workplace health for that of the Occupational Safety and Health Administration; its own judgment on climate change for that of the Environmental Protection Agency; and its own judgment on student loans for that of the Department of Education.