Over the past few years, tobacco legislation has resembled a patchwork quilt across the United States: Tobacco-buying age rules that don't cross state borders. Flavor ban ordinances in one municipality, but not in another 10 minutes away. It was enough to make even the most seasoned tobacco retailer's head spin.

Uniformity began to creep into the landscape in late 2019. On Dec. 20 of that year, former President Donald Trump signed legislation to amend the federal Food, Drug and Cosmetic Act and raise the federal minimum age on the sale of tobacco products from 18 to 21. [...]