CITADEL PUSHES BACK AS SEC MOVES TO SCRAP KEY STOCK-MARKET RULE
SEC proposal would eliminate the 20-year-old Order Protection Rule as critics warn of weaker price protection and reduced transparency for retail investors.
August 21, 2026
The Securities and Exchange Commission is proposing to eliminate one of the central protections built into the modern U.S. stock market.
And one of the firms warning against the move is Citadel Securities.
On June 11, the SEC unanimously proposed rescinding Rule 611 of Regulation NMS, commonly known as the Order Protection Rule or trade-through rule, together with Rule 610(e), which restricts locked and crossed markets.
The public-comment period closed August 17.
Citadel Securities subsequently urged the SEC to reconsider, warning that eliminating Rule 611 could increase the internalization of stock orders, reduce liquidity displayed on public exchanges, weaken price discovery and ultimately harm retail investors.
Reuters reported that Citadel described the SEC’s economic analysis supporting repeal as “fatally flawed.”
For a rule most retail investors have probably never heard of, the consequences could be significant.
WHAT RULE 611 DOES
Rule 611 was adopted as part of Regulation NMS in 2005.
In simplified terms, it prevents trading centers from executing certain stock trades at prices inferior to better protected quotations displayed elsewhere.
Suppose one protected market is offering shares at:
$10.00
while another is offering the same shares at:
$10.01.
Subject to exceptions in the rule, the second market generally cannot simply execute a purchase at $10.01 while ignoring the protected $10.00 quotation.
That would constitute a trade-through.
Rule 611 does not guarantee every investor the best conceivable price, nor is it the same thing as a broker’s separate best-execution obligation.
But it establishes an objective protection against certain inferior executions.
The SEC is proposing to remove it.
WHY THE SEC WANTS CHANGE
SEC Chairman Paul Atkins argues that the market has changed dramatically since Regulation NMS was adopted more than twenty years ago.
Modern trading systems can evaluate multiple venues in fractions of a second, while the existing regulatory structure has contributed to complicated routing arrangements, connectivity requirements and costs.
The SEC believes eliminating Rules 611 and 610(e) could simplify market structure, reduce regulatory burdens and allow greater competition and technological innovation.
That argument has merit.
A market rule should not survive forever simply because it has existed for twenty years.
The question is what happens when it disappears.
EVEN THE SEC SEES A POTENTIAL PROBLEM
The SEC’s own proposal identifies one consequence that deserves particular attention from retail investors.
Many retail stock orders are not executed on public exchanges. They are instead routed to wholesale market makers that may execute those orders internally.
Without Rule 611, the SEC acknowledges that wholesalers:
“may begin to trade through displayed round-lot quotes”
that currently receive protection under the rule.
The Commission says this could potentially result in:
“worse prices for these orders.”
The SEC also identifies forces that could limit that outcome.
Wholesalers compete for retail order flow. Brokers evaluate execution quality. Best-execution obligations remain. New execution-quality disclosures could also make it easier to compare performance.
But that represents a significant philosophical change.
Rule 611 imposes an objective restriction on certain trade-throughs.
Without it, investor protection would depend more heavily upon competition, broker obligations, disclosure and subsequent regulatory oversight.
CITADEL WARNS ABOUT PRICE DISCOVERY
Citadel’s objection is particularly notable because the firm is one of the country’s largest wholesale market makers and handles enormous volumes of retail order flow.
According to Reuters, Citadel warned that eliminating Rule 611 could encourage additional internalization and move trading away from displayed exchanges.
That creates a broader problem.
Public exchanges do more than execute trades.
They help establish the prices against which enormous amounts of off-exchange trading are measured.
If increasing amounts of trading move away from those displayed markets, critics worry that liquidity and price discovery could deteriorate.
In other words:
The public market establishes the price.
Increasing amounts of trading can occur somewhere else.
At some point regulators have to ask whether reducing activity in the price-setting market begins to affect the quality of the price itself.
RETAIL INVESTORS PUSH BACK
Citadel is not alone.
The SEC’s public-comment file contains substantial opposition from individual investors and other market participants concerned about the consequences of eliminating Rule 611.
A central concern is the imbalance between sophisticated institutional participants and ordinary retail investors.
Institutional firms can employ sophisticated routing technology, direct market connections and proprietary market data.
The ordinary investor generally relies upon a broker to decide what happens after pressing:
BUY
or
SELL.
If an objective trade-through restriction disappears, critics argue that retail investors will become even more dependent upon brokers and wholesalers to ensure they receive appropriate execution.
The SEC believes competition and existing obligations may provide that discipline.
Opponents are asking whether “may” is good enough.
WHAT HAPPENS NEXT
The public-comment period on the proposal has now closed.
The SEC must consider those submissions before determining whether to proceed with the repeal, modify the proposal or leave the existing rules in place.
Nothing has been repealed yet.
And the debate should not be reduced to whether Rule 611 is perfect.
It isn’t.
The real question is whether the SEC can modernize an aging market structure without weakening the protections investors receive when their orders enter an increasingly automated and fragmented market.
Perhaps Rule 611 should be reformed.
Perhaps technology has made portions of it obsolete.
Perhaps competition can eventually provide better protection than the existing regulatory structure.
But before removing a rule designed to prevent certain inferior executions, there is one question regulators should be able to answer clearly:
What provides equivalent or better protection after it is gone?
For retail investors, the answer could eventually be measured in fractions of pennies.
Across billions of shares, fractions of pennies can become very large numbers.
SOURCES
U.S. Securities and Exchange Commission — Proposed Rescission of Regulation NMS Rules 611 and 610(e)
SEC proposal and rulemaking materials
U.S. Securities and Exchange Commission — June 11, 2026 announcement
SEC announcement of proposed rescission
Reuters — August 18, 2026
Citadel Securities urges SEC to reconsider proposal
SEC Public Comment File — S7-2026-20
Public comments on proposed Rule 611 repeal