S.E.C. Moves Against Day-Trading Broker SHANGHAI -- The Securities and Exchange Commission has revoked the license of a Canadian brokerage firm over failing to prevent overseas day traders that used its system from manipulating stocks in the United states. The firm, the Biremis Corporation, worked with more than 5,000 day traders in 30 countries, including China, Nigeria and Uzbekistan, allowing them to trade stocks in the United States and other markets. Biremis, which is affiliated with Swift Trade of Canada, lost its license in the United States and its two owners were barred from the securities industry. Biremis had about 5,000 traders working with it worldwide, with most of its trading operations based in China, where there are few regulations covering overseas trading. The S.E.C. said on Tuesday that from 2007 to 2010, day traders working with Biremis engaged in manipulative practices known as "layering," "gaming" or "spoofing," which involved entering trades with no intention of executing them, simply to trick other buyers and sellers into trading at unfavorable prices. The S.E.C. said Biremis and its owners ignored red flags and warnings about manipulative trading and did not act to stop it. The firm helped manage one of the world's largest groups of day traders -- people who speculate on stocks by buying and selling on the same day. In recent years, United States and Canadian trading firms like Swift, Hold Brothers and Title Trading had been recruiting young people in China to use the companies' software and capital that they supplied to make money on securities listed in the United States and other markets. Exactly how the day traders could make money trading in overseas markets was a mystery to many trading experts, since there is fierce competition and trading fees could mount. Biremis traders had access to about $2.4 billion in buying power in 2009, according to the S.E.C. But the broker had been sanctioned by regulators in several countries, including Canada and Britain. Peter Beck, 57, and Charles Kim, 40, the owners of Biremis, were fined $250,000 each and barred from the industry. Mr. Beck also helped found Swift Trade. Mr. Beck and Mr. Kim could not be reached for comment early Wednesday.