SACRAMENTO, Calif. >> A state judge on Wednesday blocked Gov. Jerry Brown’s proposed ballot initiative to reduce California’s prison population, despite warnings that her decision could effectively stall its consideration by voters until 2018.

Sacramento County Superior Court Judge Shelleyanne Chang sided with district attorneys who argued that Brown improperly bypassed normal procedures.

She barred Attorney General Kamala Harris from issuing documents — the title of the initiative and a summary of what it would do — that would let supporters begin gathering signatures for Brown’s proposal.

“The court finds that the attorney general abused her discretion,” Chang said, ruling that the amendments radically change the focus of the original initiative without allowing for necessary public comment.

“What the amendment did was the type of mischief that the Legislature had in mind” when it required that amendments to ballot initiatives be related to the original initiative, the judge said.

Friday was the deadline for Harris to act, but Chang agreed with the California District Attorneys Association and Sacramento County District Attorney Anne Marie Schubert after they sued over the ballot measure.

The ruling could delay signature-gathering for Brown’s initiative beyond this year and possibly push it to the 2018 ballot.

Chang’s ruling “makes it impossible” for proponents to put the initiative before voters this year, said attorney James Harrison, who argued on behalf of the original proponents who allowed Brown to alter their measure. That would deny voters the opportunity to consider sweeping public-safety reforms, he told reporters.

Proponents will file an emergency appeal with the 3rd appellate district or the state Supreme Court, he said. Harris’ spokeswoman, Rachele Huennekens, said the attorney general also will appeal Chang’s ruling.

The prosecutors who sued said Brown must file a new initiative instead of changing an existing proposal.

Brown amended an existing initiative that would strip prosecutors of their power to decide if juveniles should be tried as adults, leaving that decision to judges. He added amendments last month to increase sentencing credits for adult inmates and allow earlier parole for non-violent felons.

Deputy Attorney General Paul Stein said Brown met the deadline for submitting amendments that reasonably related to the initiative’s original focus, even though it was amended after the end of the public comment period.

He argued that Chang shouldn’t try to discern legislators’ intent, but merely interpret the letter of a law that he said allows even substantial late revisions.

The 2014 state law requires 30 days of public comment as a way to improve the initiative process. The same law lets initiative sponsors amend their proposal and lets the state Legislature hold hearings before measures qualify for the ballot.

Thomas Hiltachk, the attorney representing prosecutors, said lawmakers intended for amendments to be narrowly focused to fix drafting errors or to correct unintended consequences.

Brown’s sweeping revision, he said, “effectively repeals by constitutional supremacy, I think we counted up to now 40 statutes or provisions in statutes … and at least six voter-approved statewide initiatives. None of those deal with juvenile justice,” he said.

“It’s a massive policy shift” that would allow earlier parole for tens of thousands of inmates, a change that Hiltachk said left the original juvenile justice provision as a mere afterthought.