Supreme Court Justices voiced hesitation on Tuesday about upending a key legal shield that protects tech companies from liability for their users’ posts, and for how the companies moderate messages on their sites.

Justices across the ideological spectrum expressed concern with breaking the delicate balance set by Section 230 of the Communications Decency Act as they rule on the pivotal case, Gonzalez v. Google, even as some suggested a narrower reading of the liability shield could sometimes make sense.

The current case was brought by the family of an American killed in a 2015 terrorist attack in Paris. The petitioners argue that Google, through its subsidiary YouTube, violated the Anti-Terrorism Act by aiding and abetting ISIS, as it promoted the group’s videos through its recommendation algorithm. Lower courts sided with Google, saying Section 230 protects the company from being held liable for third-party content posted on its service.

The petitioners contend that YouTube’s recommendations actually constitute the company’s own speech, which would fall outside the bounds of the liability shield.

But the justices struggled to understand where the petitioner’s counsel, Eric Schnapper, was drawing the line on what counts as content created by YouTube itself.

Conservative Justice Samuel Alito at one point said he was “completely confused” by the distinction Schnapper tried to draw between YouTube’s own speech and that of a third party.

Schnapper repeatedly pointed to the thumbnail image YouTube shows users to display what video is coming up next, or is suggested based on their views. He said that thumbnail was a joint creation between YouTube and the third party that posted the video, in this case ISIS, because YouTube contributes the URL.

But several justices questioned whether that argument would apply to any attempt to organize information from the internet, including a search engine results page. They expressed concern that such a broad interpretation could have far-reaching effects the high court may not be prepared to predict.

Conservative Justice Brett Kavanaugh noted that courts have applied Section 230 consistently since its inception in the 1990s and pointed to the amici briefs that warned overhauling that interpretation would cause massive economic consequences for many businesses, as well as their workers, consumers and investors. Kavanaugh said those are “serious concerns” Congress could consider if it sought to rework the statute. But the Supreme Court, he said, is “not equipped to account for that.”

“You’re asking us right now to make a very precise predictive judgment that ‘Don’t worry, that it’s really not going to be that bad,'” Kavanaugh told U.S. Deputy Solicitor General Malcolm Stewart, who was arguing the high court should send the case back to the lower court for further consideration. “I don’t know that that’s at all the case. And I don’t know how we can assess that in any meaningful way.”

When Stewart suggested that Congress could amend 230 to account for changes in the reality of the internet today, Chief Justice John Roberts pushed back, noting “the amici suggests that if we wait for Congress to make that choice, the internet will be sunk.”

Even conservative Justice Clarence Thomas, who has openly written that the court should take up a case around Section 230, seemed skeptical of the petitioners’ line in the sand. Thomas noted that YouTube uses the same algorithm to recommend ISIS videos to users interested in that kind of content, as it uses to promote cooking videos to those interested in that subject. Plus, he said, he sees those as suggestions, not affirmative recommendations.

“I don’t understand how a neutral suggestion about something that you’ve expressed an interest in is aiding and abetting,” Thomas said.

The justices had tough questions for Google too, wondering if the liability protections are quite as broad as the tech industry would like to believe. Liberal Justice Ketanji Brown Jackson, for example, had a long back and forth with Lisa Blatt, counsel arguing on behalf of Google, about whether YouTube would be protected by Section 230 in the hypothetical scenario in which the company promotes an ISIS video on its homepage in a box marked “featured.”

Blatt said publishing a homepage is inherent to operating a website so should be covered by Section 230, and that organization is a core function of platforms, so if topic headings can’t be covered, the statute basically becomes a “dead letter.”

Liberal Justice Elena Kagan suggested it’s not necessary to agree completely with Google’s assessment of the fallout from altering 230 to fear the potential consequences.

“I don’t have to accept all of Ms. Blatt’s ‘the sky is falling’ stuff to accept something about, ‘Boy, there’s a lot of uncertainty about going the way you would have us go,’ in part just because of the difficulty of drawing lines in this area,” Kagan told Schnapper, adding the job may be better suited for Congress.

“We’re a court, we really don’t know about these things,” Kagan said. “These are not like the nine greatest experts on the internet.”

Cathy Gellis is an independent attorney in the San Francisco Bay Area who filed an amicus brief on behalf of a person running a Mastodon server, as well as a Google-funded startup advocacy group and a digital think tank. She told CNBC that briefs like hers and others seemed to have a big impact on the court.

“It would appear that if nothing else, amicus counsel, not just myself, but my other colleagues, may have saved the day because it was evident that the justices took a lot of those lessons on board,” Gellis said.

“And it appeared overall that there was not a huge appetite to upend the internet, especially on a case that I believe for them looked rather weak from a plaintiff’s point of view.”

Still, Eric Goldman, a professor at Santa Clara University School of Law, said while he felt more optimistic on the outcome of the Gonzalez case, he remains concerned for the future of Section 230.

“I remain petrified that the opinion is going to put all of us in an unexpected circumstance,” Goldman said.

On Wednesday, the justices will hear a similar case with a different legal question.

In Twitter v. Taamneh, the justices will similarly consider whether Twitter can be held liable for aiding and abetting under the Anti-Terrorism Act. But in this case, the focus is on whether Twitter’s decision to regularly remove terrorist posts means it had knowledge of such messages on its platform and should have taken more aggressive action against them.

Conservative Justice Amy Coney Barrett asked Schnapper how the decision in that case could impact the one in the Google matter. Schnapper said if the court ruled against Taamneh, the Gonzalez counsel should be given the chance to amend their arguments in a way that fits the standard set in the other case.

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