The Setup: Structural Relationships
At the time of the January 2021 frenzy, Citadel Securities was Robinhood's primary market maker, processing the vast majority of Robinhood's order flow through PFOF arrangements. Separately, Citadel Advisors (the hedge fund) had invested approximately $2 billion to rescue Melvin Capital — a fund with a significant short position in GameStop. Although Citadel Securities and Citadel Advisors operate separately with regulatory information barriers, both entities were helmed by Kenneth Griffin and had obvious incentives affected by GME's price.
The Trading Halt
On January 28, 2021, Robinhood halted purchases of GameStop, AMC, and other heavily-shorted stocks. Robinhood cited capital and margin requirements from the DTCC as the reason. The halt came as retail investors were driving GME's price to extraordinary heights, inflicting massive losses on short sellers including Melvin Capital. The timing — a purchase halt, not a trading halt — exclusively harmed buyers and benefited short sellers.
Congressional Scrutiny
The House Financial Services Committee convened a hearing with Kenneth Griffin, Robinhood CEO Vlad Tenev, and others. Griffin testified that Citadel Securities had no role in Robinhood's decision to halt trading. Congressional investigators found no evidence of direct communication between Citadel and Robinhood about the halt. However, the structural conflict — Citadel as the market maker for Robinhood's retail orders while also being the rescuer of the short-selling hedge fund — was never adequately addressed.
The Unanswered Questions
The GameStop episode exposed structural conflicts that remain unresolved. Citadel Securities continues to be the primary market maker for major discount brokers. The hedge fund and market-making operations remain under the Griffin umbrella. Regulatory reform efforts have stalled. And millions of retail investors continue to trade through a system where the same firm that profits from their order flow is also, in many cases, the firm whose hedge fund operations have opposing market positions.