As Katharine Silbaugh sees it, one mark of a good public policy is being both big and small: big in its potential impact, small in its disruption to people’s lives. Silbaugh, a lawyer and one of the 240 elected “town meeting members” who make up local government in the picturesque Boston suburb of Brookline, thinks she’s managed to thread that needle with a recently passed ordinance unlike any other in the country.

The ordinance, co-sponsored by Silbaugh and pharmacist and fellow town meeting member Anthony Ishak, ties the right to buy tobacco not to age, but to birth date. At the federal level, Americans can buy cigarettes, vapes and cigars when they turn 21. But in Brookline, anyone born after Jan. 1, 2000 will never be able to legally buy tobacco or vapi…