‘Our states are losing massive sales-tax revenues that we need for education, health care, and infrastructure,” South Dakota’s Attorney General Marty Jackley told the U.S. Supreme Court Tuesday. His state’s Supreme Court opined that sales tax revenues have “declined.” The state Legislature, citing its own “finding” to this effect, enacted a law requiring out-of-state retailers to collect sales tax on purchases shipped to South Dakota.
But in addition to running counter to decades of precedent governing interstate commerce—which...