A judge has ordered California elections officials to expand voter registration throughout the state to county welfare offices and student financial aid centers.

In a lawsuit by advocates for the elderly, the disabled and the American Civil Liberties Union, San Francisco Superior Court Judge Ethan Schulman ruled last week that Secretary of State Alex Padilla was not complying fully with the National Voter Registration Act of 1993. That law requires states to sign up new voters at all offices that provide either public assistance or state-funded services for people with disabilities.

In response to the suit, the ACLU said, Padilla agreed last year to designate disability service offices at University of California, California State University and community college campuses as voter registration agencies, as well as state Social Services offices that provide assistance to the blind. But Padilla refused to go further, arguing that the public assistance requirement covered only agencies that provide federal aid, like food stamps and family welfare grants, and not programs like student financial aid that are funded solely by the state and local governments.

Schulman disagreed, saying the law expressly referred to “all offices in the state that provide public assistance.” He said those include county offices that provide general-assistance benefits to poor adults who are ineligible for federal family aid, and to California Student Aid Commission offices that provide financial aid to needy college students under five programs.

The judge rejected advocates’ arguments that voter registration must also take place at offices of the state Department of Education or at 33 offices that distribute federal funds for assistance to the elderly. Although those offices take part in public-assistance programs, they do not directly provide benefits to the public, but instead transfer their funds to local schools and community programs, Schulman said.

The ACLU said county welfare offices covered by the ruling receive applications for benefits from nearly 300,000 Californians each year, and the Student Aid Commission got more than 1.5 million applications for financial assistance last year.

“Millions of Californians faced barriers to voter registration due to Secretary Padilla’s inaction,” ACLU attorney Raul Macias said Wednesday. He said he hoped Schulman’s ruling would be “a wake-up call for the secretary’s office that we need increased compliance” with the federal voting law.

Padilla’s office said it was reviewing the ruling.

Bob Egelko is a San Francisco Chronicle staff writer. Email: begelko@sfchronicle.com Twitter: @BobEgelko