Nearly three decades have passed since the city stopped issuing permits for short-term rentals — bed-and-breakfast establishments and transient vacation units — except in hotel-resort zones. The freeze contains Oahu’s legal inventory today to about 800 TVUs and just 44 B&B operations.

Of course, it’s no secret that due to weak enforcement of weak regulation, the emergence of easy online advertising through brokers like Airbnb, and other reasons — spurred by a record-breaking streak in visitor arrivals now spanning at least six years — the inventory of illegal vacation rentals is exploding.

By some counts there are well over 20,000 scofflaws in Hawaii, mostly on Oahu. By failing to crack down on illegal operations or expand the legal inventory, the city has missed out on megabucks in fines or tax revenues, respectively, tied to this thriving underground industry.

Mayor Kirk Caldwell acknowledges that the proliferation is ruining the character of some neighborhoods and impacting the affordability of homes for residents. On the other hand, he notes that a sweeping shutdown of illegal vacation rentals could significantly slow the flow of visitor arrivals, touching off serious economic concerns for our tourism-dependent state.

In an effort to balance the matter, Caldwell, in his State of the City speech last week, pitched a plan that makes room for more legal B&Bs and TVUs, but only if operators are also the property owners, abide by tougher guidelines, and pay higher property taxes. The plan, which echoes elements of proposals the City Council is already wrestling with, is a step in the right direction. Whether it succeeds in establishing effective regulation will hinge largely on enforcement.

Key to the plan is a requirement for all short-term rentals to include a city-assigned registration number in all advertising materials. Eligibility should be limited to owner-occupants — property owners who also hold homeowners’ exemptions — as a means to phase out absentee operations that have resulted in noise- and traffic-related headaches in otherwise quiet neighborhoods.

The registration number would allow cross-checking city code compliance for inspectors to zero in on illegal operations. With it, Caldwell said, the city can make good on a long-overdue enforcement bite without expanding the current roster of about 15 inspectors in the Department of Planning and Permitting (DPP). That’s doubtful, though, given the plan’s vision for expanding the legal inventory:

>> Hosted bed-and-breakfast operations would be allowed in residential areas, apartment districts, business districts and mixed use districts, including every street in Waikiki. Inside those boundaries, there would be no limit on the count of operations.

>> The unhosted TVU count, meanwhile, would be limited to 1 percent of all available housing units in each of the nine planning regions as defined in the city General Plan. They would be banned from areas zoned for single-family residential but allowed in apartment and business mixed-use zones.

Both types of rentals, which limit stays to fewer than 30 days, would see no change in the number of units allowed per household, which is two, or in the parking requirement of one stall for each unit. However, both would see an increase in property taxes, with higher rates rightly imposed on TVU operations. Nearly all complaints DPP responds to are about unhosted TVUs. These operations should be saddled with a tax burden set at the same rate as hotels and resorts.

While the city can now impose fines on legal operations and ferret out illegal rentals, the current law requires DPP inspectors to essentially catch scofflaws in the act. Stiffer penalties are needed to help put a quicker end to law-flouting operations.

Under Caldwell’s plan, anyone caught advertising illegally would be hit with a penalty of $25,000 per day starting seven days after the first notice of violation, and later ramping up to $100,000 a day. Failure to pay would result in liens against the rental property and other penalties. That’s expensive — and consequential — enough to make any would-be underground operator think twice.

However, unless enforcement is delivered in a swift and consistent manner, any new law — like the current law — will be, well, laughable. According to DPP’s most current figures, in 2016 its inspectors were tasked with handling some 3,000 complaints tied to short-term rentals. That resulted in 90 notices of violation and about 70 cases in which problems were corrected. It’s difficult to imagine how the city could effectively manage a potentially larger inventory of short-term vacation rentals without a larger, vigilant staff.

Still, Caldwell and Council members must persevere on this thorny issue. The city cannot afford to let another decade pass without striking a viable balance between collecting taxes owed and deterring the rocketing rise of illegal vacation rentals.