Rules, Regulators and the Licence to Trade

On 14 April 2026 the Securities and Exchange Commission gave accelerated approval to a FINRA rule change that ended one of the best-known constraints on American traders. Since 2001 (verify) a margin customer who made four or more day trades in five business days had been designated a pattern day trader and needed $25,000 of equity to keep going. FINRA's amendments to Rule 4210 (SR-FINRA-2025-017; Exchange Act Release No. 105226) removed the day-trade count, the $25,000 minimum and the day-trading margin requirements "in their entirety", and replaced them with intraday margin standards that took effect on 4 June 2026, with brokers allowed to phase them in until 20 October 2027 (FINRA Regulatory Notice 26-10). A rule usually dated to the dot-com day-trading boom, which had pushed small accounts toward cash accounts, futures, offshore brokers and, after 2020, proprietary-trading "challenges", was gone.

Nine months earlier, on 3 July 2025, a regulator on the other side of the world had shown the opposite power. The Securities and Exchange Board of India issued an ex-parte interim order barring the group entities of Jane Street, the New York trading firm, from Indian securities markets and impounding ₹4,843.57 crore as alleged unlawful gains from intraday manipulation of the BANKNIFTY and NIFTY indices on options-expiry days. Jane Street deposited the sum in escrow on 14 July, was allowed to trade again on conditions from 21 July and disputes the findings. India had reportedly been more than 10% of its 2024 revenue (Bloomberg, reported). One rule change opened a door for millions of small accounts; one order closed a market to one of the most profitable trading firms in the world.

This chapter is about the frame around the edge equation. Rules act on all four factors: they create some edges and abolish others, set how much a trader may lose before the system stops them, decide what execution costs and who may connect to an exchange, and impose some discipline from outside. And they add a condition that sits in front of the other four, the licence to trade. A firm that loses its registration, its clearing or its market access has no edge, whatever its models say.