Citadel Securities urges SEC to reconsider stock-trading rule proposal

Citadel Securities, one of the largest market makers in the world, is pushing back hard against the SEC’s plan to eliminate a foundational stock-trading rule that has governed US equity markets for more than two decades. In a comment letter submitted on August 17, 2026, the firm founded by Ken Griffin argued that the SEC’s proposal to rescind Rule 611 of Regulation NMS, the so-called trade-through rule, could reduce liquidity, weaken price discovery, and leave retail investors worse off. The firm didn’t mince words, calling the agency’s economic justification for the change “fatally flawed.” What Rule 611 actually does Rule 611 is part of Regulation NMS, a package of rules the SEC adopted in 2005 to modernize and bring greater transparency to US equity markets. The rule’s core function is deceptively simple: it prevents brokers from executing a stock trade at a price worse than the best available price displayed on another exchange. On June 11, 2026, the SEC, under Chairman Paul Atkins, proposed eliminating Rule 611 along with a related provision, Rule 610(e). The agency’s argument centered on the idea that these protections have become unnecessary in today’s faster, more competiti...