In a way, the legislation has a head start: Last year, in an effort to bring down textbook costs, Mr. Steinberg won passage of a law requiring free online textbooks for the 50 most popular introductory college courses, and in the process created a faculty panel — three members each from the University of California, California State University and the community college system — to choose materials.

The new legislation would use that panel to determine which 50 introductory courses were most oversubscribed and which online versions of those courses should be eligible for credit. Those decisions would be based on factors like whether the courses included proctored tests, used open-source texts — those available free online — and had been recommended by the American Council on Education. A student could get credit from a third-party course only if the course was full at the student’s home institution, and if that institution did not offer it online.

Despite the element of faculty control that would be built into the process, it is not likely to sit well with faculty.

“I think it’s going to be very controversial,” said Josh Jarrett, a higher education officer at the Bill and Melinda Gates Foundation, which finances research on online education. “The decision to award credit has been one of those solemn things that the faculty hold very dear. But it could be a catalyst for widespread change, driving community colleges where they turn away a lot of students to move quickly to put more of their own courses online, and charge tuition, to keep their students from taking the courses elsewhere.”

The trend to use educational resources available free online is moving at a gallop, nationwide. This week, the University of California, Irvine, announced that it was making its chemistry videos and lectures available free online — albeit not for credit. And David Wiley, a pioneer of online education, started a new company, Lumen Learning, to work with colleges shifting toward open-source textbooks and to create degree programs that would use only open-source materials.

In putting together the new legislative proposal, Mr. Steinberg worked with Dean Florez, a former California Senate majority leader who is the president of the 20 Million Minds Foundation, which works for open-education resources. Mr. Florez said that the online courses would supplement — but never supplant — the classes taught at California’s public colleges, so that students would not be delayed by bottlenecks. His own son had to wait three semesters at Santa Monica Community College to get into a math class he needed, he said.

But Lillian Taiz, the president of the California Faculty Association, said that she thought it was too soon to conclude that online classes from third-party providers were a good substitute for the classes at state institutions.