TikTok is back in a Washington, DC courthouse discussing the US law that — at least on paper — effectively banned the app. But this time, it’s serving as a witness for the government, not fighting against it.

On Wednesday, TikTok’s head of operations and trust and safety Adam Presser testified in the Federal Trade Commission’s antitrust trial against Meta, in the same courthouse where a panel of judges ruled that the government could expel TikTok from the country. Presser’s role in the Meta trial was to explain the ways in which TikTok competes (or doesn’t) with Meta’s services in a market the FTC has defined as personal social networking — a category the FTC says contains only Meta’s services, Snapchat, and a small app called MeWe.

Lawyers for both the FTC and Meta brought up filings TikTok made in its own litigation against the 2024 divest-or-ban law, which required Chinese parent company ByteDance to sell its US business. (President Donald Trump has used dubious legal measures to extend the deadline for enforcement twice, leaving TikTok’s service providers facing the potential for billions of dollars in penalties while saying he’s working on a deal.) The FTC pointed to a TikTok statement warning that its unique services couldn’t be easily replaced in the US — in other words, the agency argues, it’s not interchangeable with an app like Meta’s Instagram. Many creators who opposed the law said they’d lose or have to shut down their businesses if TikTok went away, because Instagram does not give them the same ability to monetize or reach a sustainable scale.

Meta, on the other hand, pointed to statements TikTok made about what might happen once the ban took effect. TikTok warned that even a temporary ban “would cause significant and irreversible harms to our business and our brand.” The company said it would lose users and creators to other platforms, and some would be unlikely to come back even if the restrictions were later lifted. One of the apps that stood to gain? Instagram.

Meta made a similar point earlier in trial, when it showed that after TikTok briefly took itself offline in the US around the divestment deadline, Instagram and Facebook engagement spiked — far more than Snapchat’s.

Meta is also trying to draw parallels between the support ByteDance provides TikTok (which is based partly on an app called Musical.ly that it acquired in 2017) and the resources Meta gave to Instagram that allowed it to grow to the size it is today. It’s aiming to counter the FTC’s narrative that Instagram was simply acquired to neutralize a competitor and wasn’t meaningfully helped by the deal in ways it couldn’t have eventually accomplished itself.

TikTok has warned that should it be separated from ByteDance, it would take years to replicate the systems needed to maintain the app and keep it running reliably, and content moderation for a US-only app could run unsustainable costs. Meta has argued that it similarly provided Instagram with valuable resources that made it safer and more reliable for users much more quickly than it would have been able to do on its own. The FTC, however, argues that Instagram would have been able to figure out independent solutions for those issues and been able to succeed without Meta’s help.

Ultimately, Trump’s delay of the full impact of the ban has halted the natural experiment that would tell us where users would turn without TikTok. And Meta’s trial might be over before any deal is made.