Last summer, a bipartisan group of House members from Pennsylvania wrote federal agencies complaining that proposed guidelines restricting the marketing of unhealthy food to children marked “an alarming regulatory overreach.” They emphasized their sugary roots in “the leading confectionary producing state in the nation.” 

Indeed, Pennsylvania is home to the 117-year-old Hershey Company, maker of the ubiquitous Hershey’s kiss. But what the lawmakers from the Keystone State didn’t say was that they had other “constituents”—out-of-state campaign cash constituents, many of them Washington-based trade associations. 

The massive lobbying push by food and media interests against the controversial guidelines ...