Barack Obama may have done too little when he was president to counter Russia’s subversion of our democracy on social media. Now, however, he’s trying to make up for lost time.

The former president spoke at Stanford University on April 21 to lay out his vision for fighting disinformation on the Internet. His focus on the subject is fitting; the dusk of his administration marked a turning point from techno-optimism to pessimism after election interference revealed how easily malicious actors could exploit the free flow of information. But whatever blame the White House deserved in 2016 for failing to speak publicly about or retaliate against Moscow’s incursions, Congress and companies have fallen even shorter in the years since by failing to enact reforms — or reform themselves.

That’s where Mr. Obama’s ideas come in. His diagnosis is on target. The Internet has given us access to more people, more opportunities and more knowledge. This has helped activists drum up attention for overlooked causes. It has also enabled the nation’s adversaries to play on our preexisting prejudices and divisions to sow discord. On top of that, “an instant, 24/7 global information stream,” from which audiences can pick and choose material that confirms their biases, has deepened the social divides that bad actors seek to exploit.

The prescription is more complicated. Mr. Obama starts where most lawmakers are stuck: Section 230 of the Communications Decency Act, which gives platforms immunity from legal liability for most third-party posts. He suggested a “higher standard of care” for ads than for so-called organic content that everyday users post. This would strike a sensible balance between eviscerating Section 230, making sites accountable for everything they host, and doing nothing. Yet Congress would have to act with care: Any government rule that would encourage private corporations to punish harmful but legal speech treads on tricky First Amendment territory.

Mr. Obama identified another problem with the Section 230 talk: homing in on what material platforms do and don’t take down risks missing how the “very design” of these sites privileges polarizing, inflammatory posts. With this, Mr. Obama adds something vital to the mainstream debate over social media regulation, shifting attention away from a debate about whack-a-mole content removal and toward the sites’ underlying structures. His specific suggestions, while fuzzy, also have promise — from slowing down viral material to imposing transparency obligations that would subject social media companies’ algorithms to scrutiny from researchers and regulators.

Mr. Obama calls this “democratic oversight.” But the material companies reveal could be highly technical. Ideally, it would get translated into layman’s terms so that everyday people, too, can understand how decisions so significant in their daily lives and the life of the country are made. Then, they could demand something better.