Law enforcement officials from Northern California said they will refuse to assist federal authorities in the upcoming sweeps that aim to capture more than 1,500 illegal immigrants, the San Francisco Chronicle reported Wednesday.

The paper, citing an anonymous source, reported about a planned operation to be conducted by the U.S. Immigration Customs and Enforcement agency. The report did not specify a date, but said it will be conducted in the near future.

Law enforcement officials told the paper they have not been notified as of Wednesday, but said they would not provide support.

Oakland Mayor Libby Schaaf told reporters that police in her city will not assist ICE officials if the report on the raids is accurate.

Federal officials’ ability to work with local jurisdictions was curtailed on Jan. 1st, after a new California law – SB54 – came into effect that limited inter-agency cooperation. The law officially made California the first “sanctuary state.”

Thomas Homan, the acting director of ICE, said last month that federal immigration officials are prepared to protect local communities in California if local officials refuse to do so.

Proponents of the law have argued that sanctuary laws are necessary to establish trust between immigrants and local law enforcement.

The Oakland City Council on Tuesday passed a resolution that ends all cooperation between local police and federal immigration officials. Under the state’s law, California police are limited in their communication with federal agents on possible illegal immigrants in jail or awaiting trial.

Homan called the resolution “unconscionable” and a “danger for local communities.”

ICE has refused to comment on the operation because the agency does not release information on future operations.