The Hawaiʻi Appleseed Center for Law & Economic Justice estimates there are 23,000 vacation rentals in Hawaiʻi, and many are illegal.

Other jurisdictions have been more effective than Hawaiʻi in dealing with vacation rentals, says Madison DeLuca, a policy analyst at Hawaiʻi Appleseed.

One approach makes the advertising platforms responsible for removing illegal vacation rental listings and requires that platforms provide jurisdictions with such data as addresses of listed properties and permit and tax numbers—practices that give local enforcement teeth.

Platform liability is used in San Francisco, where only permanent residents can host vacation rentals, and they’re required to register with the city. Hosting platforms are fined if they do not remove listings that are unregistered—and therefore illegal. Peter Byrne, senior analyst in San Francisco’s Office of Short-Term Rentals, says the platforms have been cooperative and the city now has fewer than 4,000 short-term rental listings on major platforms, compared to 12,00 to 15,000 before platform liability was required.

Isaiah Feldman-Schwartz, a legal analyst with Hawaiʻi Appleseed, says platform liability disincentivizes people from illegal operations because they can’t get bookings without advertising. And it means that one person can monitor illegal activity from a computer instead of sending several people around the island to knock on doors and see if people are home, he adds.