Flávio Bolsonaro's legal team submitted a petition to Brazil's electoral tribunal, the TSE, on 16 October, seeking permission for the Rio de Janeiro senator and conservative presidential hopeful to join the ongoing proceedings that President Luiz Inácio Lula da Silva has brought against Meta. Attorneys representing Flávio moved to enter the proceedings as an interested third party in the complaint brought by Lula's campaign on 9 October.

According to a broadcast outlet's Saturday report, the campaign alleged that Meta bears responsibility for allowing paid advertisements targeting Flávio with negative content to continue circulating on its platform. According to the campaign, funding for the attack advertisements comes from both Lula's official account and outside contributors.

Attorneys representing Lula put forward the position that Meta — the parent company behind Instagram, Facebook, and WhatsApp — had not been distributing posts from Lula or those backing him. According to a court filing reported by a news outlet, Meta's handling of the matter had left both the campaign and the court repeatedly unable to make headway, a situation the document describes as an ongoing and unacceptable exercise in futility.

The petition lodged with the court calls for Meta to be prohibited from running paid negative advertisements before the runoff concludes, and for a separate restriction preventing both private individuals and corporate entities from purchasing any electoral advertising during that period. The petition further stipulates that any advertisements reinstated on Lula's profile be free of attack-style content.

Ad data drawn from Meta's publicly accessible library forms the foundation of the campaign's approach. According to the data cited, Lula's Facebook account ran 3,908 advertisements directed against Flávio between September and the reporting period, with 2,035 of the 2,624 ads launched on 9 and 10 October falling into that category. According to the same report, 423 attack advertisements remained live when the morning of 16 October arrived.

No independent cross-check against the ad library has been carried out on the figures put forward by the campaign. Those ad tallies derive solely from the campaign's own analysis of Meta's advertising library, and neither Meta nor the court has independently verified them.

In a statement to a broadcast news outlet, Meta maintained that the platform does not align itself with any side in this election or others, pushing back against allegations that its systems favour particular campaigns. The platform stated that its content policies, compliance with Brazilian electoral legislation, and processes for addressing errors would all remain in place.

Internal communications among Meta employees, reviewed by a well-known broadcaster, pointed to constraints that affected the reach of Lula's Instagram presence alongside the platform's algorithmic promotion of Flávio's Instagram profile and his WhatsApp channel. A technical restriction on Lula's verified account left it unable to promote posts through Instagram for a period spanning nearly a full day, beginning 9 October.

A judicial directive issued that Thursday — 15 October — required Meta to apply uniform treatment to both campaigns, while the company submitted a note to the court pointing to technical irregularities affecting Lula's accounts. The legal submission from Flávio's camp contends that the distribution advantage actually tilts toward Lula's operation, which it claims has drawn on paid reach for an extended stretch of time.

According to documents filed with the court and reported by a broadcast outlet, a temporary suspension of one candidate's advertising account at Meta — lasting only a matter of hours — cannot be assessed, the filing argues, without also accounting for the months during which the other candidate reportedly had paid negative content distributed against them.

Any legal judgment or financial penalty handed down in Brazil — a nation of more than 200 million people — would have direct bearing on how Meta, headquartered in the United States, structures its advertising policies across that market. At issue, too, is the extent to which a court operating outside the United States holds authority to direct how an American platform handles the placement of political advertising.

By 17 October, the tribunal had yet to announce a position on whether Flávio would be recognised as an interested party or whether any adjustment to Meta's advertisements would be directed. Questions about the volume of paid advertising each campaign may still legally place before polling day remain unresolved.

Filings from both parties now sit at the centre of the dispute — one put forward by Meta's side arguing that Lula received unfair treatment, the other lodged earlier by Lula's representatives advancing the opposite position against Meta. A presidential runoff scheduled for Sunday, 25 October, will put Lula and Flávio Bolsonaro before the Brazilian electorate.