Opinion | The court is right about Google and Twitter. But Congress has to act.

By avoiding blunt interpretations of Section 230, the law that shields online companies from liability for posts made on their platforms, the justices left the door open for more nuanced reforms — changes that could protect dissidents and innovators while also stemming the spread of dangerous content.

Section 230 of the 1996 Communications Decency Act fostered the internet as we know it by allowing digital platforms to act less like old-school publishers and more like free-for-all marketplaces for ideas. But Section 230’s limits have also become apparent as algorithms have amplified the worst ideas, including some that lead to real-world violence.

With Gonzalez v. Google and Twitter v. Taamneh, the Supreme Court had the opportunity either to shrink Section 230’s protections for tech companies and free speech — which might have stifled both innovation and political dissent online — or to wield the law to broadly shield social media companies from anything and everything awful they might put forth. The facts of the two cases were too weak for proving tech company responsibility for terrorism. By skirting Section 230, the court left it open for elected officials to address the future of the internet. Lawmakers should now find a way to balance the good the law does against the harm it permits.

Section 230’s value is evident in what it has brought forth on the internet. With people given permission to say almost anything and virtually no onus on companies to curate their posts, a thousand flowers have bloomed: political protests, family trees, how-to videos. The policy makes the internet a collective body to which everyone can contribute in real time, with no gatekeeping. But Section 230 did not anticipate the ills of algorithmic amplification. This danger from the big platforms has become too familiar, from QAnon videos queued up as recommendations on YouTube to Islamic State recruitment posts spreading on Twitter.

What’s often lost in debates about Section 230 is that it also allows and even, in theory, encourages privately owned online platforms to moderate content — to take down distasteful or harmful content no matter how loud their users cry censorship. Companies such as Twitter have no obligation to ensure freedom of speech if someone is obnoxious enough.

Some advocates of Section 230 reform go overboard in demanding that platforms moderate broad swaths of content. Excessive curation could lead to an internet that is worse than the one we have: Platforms could end up silencing any posts that might be seen as controversial — whether that’s organizing health-care access or planning a political rally. (Already, Twitter has cowered to some Indian government antidemocratic schemes, and Facebook has cooperated with police enforcing antiabortion laws.)

Extensive content moderation is also difficult and costly, and could make it hard for anyone to start or curate a new social media platform. The world could be stuck with only the existing big tech companies, and never see more innovative and public-minded start-ups.

As Justice Elena Kagan admitted in oral arguments on Gonzalez, Supreme Court justices are “not like the nine greatest experts on the internet.” (Justice Clarence Thomas nonetheless appeared to want the court to revisit 230.) Congress, though, can and should now engage technology experts and the public on these issues and find the best ways to improve Section 230.

The goal should be to balance free expression with accountability. An updated Section 230 could, for example, provide immunity only for companies that take steps to address specific kinds of harmful and illegal behavior, said Danielle Citron, a law professor at the University of Virginia. Citron pointed out that the court’s recent rulings also leave room for lower courts to hold companies liable on a case-by-case basis for product designs that endanger the public. A case against Snap, for instance, alleged that its Snapchat speed filter rewarded reckless driving.

While Thursday’s rulings have not undermined the internet, they do leave critical problems unsolved. The current system is not working well for democracy — nor is it keeping people safe. Laws and judicial decisions have yet to motivate social media companies to rein in the worst of what happens online, including not just the organization of terrorism and violence but rampant harassment, privacy invasions and hate speech.

A nuanced, legislative cure for social media’s ills is urgent. The path forward requires leadership from Congress — with help from experts and citizens who both see the internet’s promise and deeply understand its perils.