Russian anti-Kremlin campaigner Alexei Navalny has built an empire on YouTube with his high-production investigative videos that aim to reveal corruption at the country’s highest levels.

But his latest video, which waded into the murky waters of Russia’s alleged meddling in the 2016 U.S. election, has resulted in a legal tussle that could end with Russia blocking access to YouTube and Instagram, as well as Navalny’s own website, undoing the famed Putin-critic’s most powerful platform.

Navalny’s latest round of troubles began as soon he released a half-hour video last week which purports to show oligarch Oleg Deripaska — a billionaire with ties to U.S. President Donald Trump’s ex-campaign manager, Paul Manafort — hanging out on a yacht off the coast of Norway with Russian deputy prime minister Sergei Prikhodko along with a woman described by Navalny as coming from “the escort services.”

Navalny claims the lavish entertainment on the yacht amounts to a “bribe,” and what’s more, points to the relationship between Navalny and Manafort to suggest that the two Russian men may have been discussing the U.S. 2016 election. But the video provides little in the way of a smoking gun, as far as the U.S. election itself is concerned, and the only snippet of speech recorded doesn’t concern the campaign.

Instead, Navalny relies largely on a deep dive into the social media activity of the woman, who goes by the name of Nastya Rybka and who once wrote a book called “Diary of Seducing a Billionaire,” to support the video’s larger narrative about the three-day yacht trip.

Deripaska didn’t take kindly to the image of himself portrayed in Navalny’s YouTube post, however, and is fighting back in court. The Russian tycoon has already won a preliminary injunction that’s led authorities to seek to block the content the oligarch contends contains false accusations against him.

The court’s ruling Friday puts seven YouTube pages and 14 Instagram posts related to Navalny’s video on the Russian media watchdog’s blacklist, according to Russian media as well as the court’s website. Deripaska’s businesses pay half the tax revenue in the town where the court proceedings are being held, according to the Russian news website Meduza.

Now, Russia’s federal censor is giving Navalny, YouTube and Instagram until this Wednesday to remove the content or face being blocked in Russia. But it will be difficult for Russian internet service providers to selectively block those pages, meaning the blockages could be widespread, according to Russian media reports.

“It’s impossible for internet providers to block certain pages on Instagram and YouTube,” and they’ll have to block the services unless the material singled out by the watchdog is deleted, Karen Kazaryan, chief analyst at the Russian Association for Electronic Communications, an internet lobby group, told Bloomberg.

Navalny was barred from running against Russian President Vladimir Putin in an election set for this March. But in recent years he’s grown his political profile by publishing barbed videos against the likes of Russian Prime Minister Dmitry Medvedev and General Prosecutor Yuri Chaika.

The senior government official featured in the latest video, Prikhodko, said he doesn’t personally know Manafort in a statement to Russian business outlet RBC. He added that Navalny should be “answered like a man, but we will stay within the legal framework.”

The official called the allegations “just his [Navalny’s] latest attempt to stage a provocation and promote himself, indiscriminately confusing everything possible and impossible.”

Navalny said his own lawyer hasn’t been allowed to get access to the proceedings in the court at Ust-Labinsky because it’s been filed against Rybka herself, whose real name is Anastasia Vashukevich, as well as an associate of hers named Alex Lesley, who’s billed himself as a sex guru who teaches classes on seduction.

Manafort, who served as Trump’s campaign chairman before resigning , once offered to give Deripaska “private briefings” in an email to an intermediary, The Washington Post reported. A company controlled by Deripaska sued Manafort over a business deal gone wrong in New York City, in just the latest chapter of a seven-year business dispute between the two men.

A representative of Deripaska’s company, Basic Element, reached in Moscow, said nobody was immediately available to comment to VICE News about the story. But in a post on Instagram last Friday, Deripaska denied any wrongdoing.

“Outrageous false allegations appeared in social networks and Mass Media that I allegedly committed unlawful actions,” Deripaska wrote. “These allegations have nothing to do with reality, are the fruit of the imagination of a group of people and the result of a planned campaign aiming to damage my reputation.”