City uses combination of zoning laws, right of pre-emption and expropriation to have good and affordable housing supply. Policy is that land is not zoned until

City uses combination of zoning laws, right of pre-emption and expropriation to have good and affordable housing supply. Policy is that land is not zoned until it's acquired by the city, which will then sell and lease lots - old landowners can't get huge windfalls from city growth and lease contracts force to build in allotted time.