San Francisco may revise its latest attempt to crack down on vacation rentals in private homes, hoping to stave off issues raised in a lawsuit filed by Airbnb that seeks to halt new enforcement measures.

Supervisors David Campos, Aaron Peskin, Eric Mar and John Avalos introduced new language at Tuesday’s Board of Supervisors meeting to update a get-tough amendment that the supervisors passed unanimously in June. The June amendment, which is now facing legal challenges from Airbnb, was scheduled to take effect July 27. Its enforcement is on hold pending a judge’s ruling on Airbnb’s request for a temporary injunction, which will be heard in early September.

The latest revision, which must now go through the legislative process, directly addresses issues Airbnb raised in its lawsuit, which said the city was violating the First Amendment, the Communications Decency Act and the Stored Communications Act.

The ultimate aim of both sets of amendments is to impose steep fines and criminal penalties to hold services like Airbnb, HomeAway and FlipKey accountable when vacation-rental listings lack the city’s mandated registration number for hosts. Only about 1,472 hosts, out of many thousands, have met a requirement to register with San Francisco before renting rooms or homes to travelers.

Potential penalties

The newest revision says those consequences would kick in only once a hosting service accepts a fee for booking a tourist to stay in an unregistered home. In the previous version, companies were on the hook for up to $1,000 a day per listing just for showcasing unregistered properties. Airbnb said that was a penalty for publishing content and therefore a violation of the federal Communications Decency Act, which shields Internet companies from liability for user-generated material. The latest update would remove the prohibition on displaying unregistered listings — but companies would be fined up to $1,000 each time an unregistered property is booked by a guest.

“These commonsense amendments aim to address some of the legal arguments that Airbnb has made in its lawsuit, and they strengthen the city’s legal position,” Campos said. “I think these amendments make the lawsuit moot.”

“The introduction of today's amendment acknowledges the legal infirmities with the city's recent changes to the short-term rental law,” Airbnb said. “The fact remains that the ordinance as it stands today violates federal law, and these new proposed amendments still wouldn't resolve the legal shortcomings that were raised in our complaint. We remain hopeful that we can work together to find solutions that address our shared policy concerns.”

The revision would allow the city’s Office of Short-Term Rentals to subpoena records from hosting services when it discovers possible violations of the city’s vacation-rental laws. Airbnb’s lawsuit said it could not legally provide information on its hosts without being subpoenaed.

In another change, companies like Airbnb, HomeAway and FlipKey would have to submit monthly affidavits affirming that all their guest stays in San Francisco were in “lawfully registered” properties. The update would also require the companies to keep three years’ worth of records on hosts and guest stays in San Francisco.

Possible exemptions

While Airbnb and FlipKey handle all transactions for their hosts, HomeAway and its VRBO subsidiary function more like classified-listing sites, similar to Craigslist. That could exempt HomeAway from the new requirements.

“If a platform does not get a fee for booking services, it would be outside the purview” of the revised law, said Robb Kapla, a deputy city attorney.

Expedia’s HomeAway and TripAdvisor’s FlipKey had expressed interest in joining Airbnb’s lawsuit against the city. U.S. District Judge James Donato gave them until Tuesday to file motions. Although sources said they were expected to so, those motions had not been submitted by late Tuesday afternoon. The companies did not respond to requests for comment.

Carolyn Said is a San Francisco Chronicle staff writer. Email: csaid@sfchronicle.com Twitter: @csaid