Have any members of Congress been convicted of insider trading or treason in recent U.S. history?

1. One clear insider-trading conviction of a former member: Stephen Buyer

Federal prosecutors in the Southern District of New York announced that former Indiana Rep. Stephen Buyer was convicted by a jury of securities-fraud counts tied to two insider-trading schemes and sentenced to 22 months in prison on September 19, 2023 ^[1]. The Justice Department statement says Buyer used stolen, material non-public information obtained through consulting work to place profitable trades ahead of public announcements in 2018 and 2019 ^[1]. This is the most concrete, recent example in the sources of a person who served in Congress later criminally convicted for insider trading.

2. Broader pattern of concern — violations of disclosure rules, not always criminal prosecutions

Multiple watchdog groups and news investigations document frequent failures by members of Congress to comply with the STOCK Act’s disclosure rules and other ethical standards, producing many allegations and administrative complaints but comparatively few criminal prosecutions ^{[4] [5] [6]}. Business Insider and other outlets identified dozens of members who failed to timely report trades required under the STOCK Act; Campaign Legal Center and Brennan Center reporting argue enforcement has been spotty and penalties are often nominal ^{[4] [5] [7]}. Those findings explain why public concern is high even where criminal convictions are rare ^[5].

3. STOCK Act: criminal law exists, but prosecutions under it are sparse

The Stop Trading on Congressional Knowledge (STOCK) Act of 2012 clarifies that members of Congress are not exempt from federal insider-trading prohibitions and expanded disclosure timelines and penalties ^{[8] [6]}. Yet analysts note the high legal bar to proving insider trading and report that, as of recent years, there had been few or no prosecutions directly under the STOCK Act itself — enforcement often relies on existing securities laws and is legally challenging ^{[9] [6]}. That legal difficulty helps explain why reporting finds many disclosure violations but relatively few criminal convictions ^[9].

4. Treason convictions of members of Congress: essentially nonexistent in modern practice

Treason prosecutions in the United States are vanishingly rare. Sources report only a small number of treason cases across American history, with very few convictions; since the mid-20th century there has been only one high-profile treason indictment (Adam Gadahn in 2006), and sources emphasize that treason charges are seldom brought and hard to prove ^{[2] [10]}. The Constitution imposes strict evidentiary rules — including testimony of two witnesses to the same overt act or confession in open court — and the statutory framing has made treason prosecutions exceptional ^{[3] [11]}. Available sources do not mention any modern treason convictions of sitting or former members of Congress.

5. Why insider trading allegations are more common than treason charges

Insider trading inquiries usually arise from financial disclosures, market movements, or whistleblowers and are addressed through securities laws, while treason requires proof of levying war against the U.S. or adhering to its enemies — a far narrower, higher-threshold crime ^{[5] [12]}. Watchdogs point to systemic problems: the timing and frequency of congressional trades, late disclosures, and an enforcement regime they describe as opaque or weak — problems that produce political outrage and civil or administrative complaints even when criminal prosecution is uncommon ^{[5] [7] [13]}.

6. Competing perspectives and limitations of available reporting

Watchdog groups such as Campaign Legal Center and think tanks press for stricter rules or a ban on trading by lawmakers, citing repeated disclosure failures and the perception of unfair advantage ^{[13] [6]}. Journalistic investigations (Business Insider, Brennan Center) document many disclosure lapses and allege enforcement scarcity ^{[4] [5]}. By contrast, reporting from legal explainer outlets stresses the practical difficulty of proving criminal insider trading under existing law and notes the rarity of successful STOCK Act prosecutions specifically ^{[9] [6]}. Available sources do not provide a comprehensive list of every allegation or every outcome, so there may be other administrative sanctions or plea deals not detailed here.

7. Bottom line for your question

Based on the provided reporting and government statements, at least one former member of Congress — Stephen Buyer — was criminally convicted and sentenced for insider trading in recent U.S. history ^[1]. Treason convictions of members of Congress are essentially nonexistent in modern times; treason prosecutions overall are rare and carry especially stringent evidentiary rules ^{[2] [3]}. Available sources do not mention any modern treason convictions of members of Congress.