A federal court decision will bar Portland City Hall indefinitely from enforcing its ordinance requiring owners of unreinforced masonry building to post warnings that buildings "may be unsafe" in the event of an earthquake.

The May 30 preliminary injunction will apply until a final decision in the case, unless another court overrules the decision. A previous injunction had been put in place when the city moved in February to revise last year's ordinance.

The case, filed in U.S. District Court in Portland, last year seeks to overturn the city's requirements both to post the placards on buildings and warn prospective tenants of the dangers of being inside an unreinforced masonry building in a seismically active zone. The ordinance was passed last year at the urging of Mayor Ted Wheeler and revised in February under City Commissioner Jo Ann Hardesty.

The case stems from a First Amendment claim that it would be a violation of the building owners' free speech requirements to make them post such warnings.

"Plaintiffs have demonstrated a substantial likelihood of success on their First Amendment Claim and enjoining enforcement of the Ordinance is necessary to prevent violations of Plaintiffs' constitutional rights," Judge John Acosta writes in the decision. "Plaintiffs have demonstrated that they will suffer imminent irreparable harm if they are required to comply with the Ordinance, and that the balance of equities tips favors Plaintiffs and it is in the public interest to prevent the violation of Plaintiffs constitutional rights."

Wheeler, Hardesty and the city attorney did not immediately respond to requests for comment.