Upon the death of Nelson Ku in January 2007, Lee was nominated to finish Ku's term in office. After Taipei County Council member Wu Shan-jeou was shot and killed, Lee argued for amendments to the Statute Regulating Firearms, Ammunition, Knives and Other Deadly Weapons, favoring harsher penalties. During Ma Ying-jeou's 2007 corruption case, Lee petitioned the Ministry of Justice to rule on the status of special allowance funds Ma was alleged to have used as income. Lee was later appointed to the Control Yuan and began a formal examination of corruption charges against Chen Shui-bian. In 2009, the agency found that two Special Investigation Panel investigators had contacted Chen Shui-bian as the corruption probe continued. The first vote to impeach State Public Prosecutor-General Chen Tsung-ming in relation to the Chen Shui-bian case was held in January 2010, and failed. Three weeks later, a second vote on the impeachment of Chen Tsung-ming passed, and Chen subsequently resigned his post. Lee was also involved in investigations of corruption within law enforcement in Taipei County and Chiayi City. He led the 2009 impeachment of former Transportation MinisterLin Ling-san, who was found to have made illegal investments in Taiwan High Speed Rail. Lee was responsible for a 2010 investigation that found Taiwan's immigration system had held foreign nationals longer than legally permitted. Facilities for foreigners detained by Taiwan were also of substandard quality. In October, the Control Yuan impeached judges Hsiao Yang-kuei of the Supreme Court and Kao Ming-che of the High Court, at the suggestion of Huang Wu-tzu and Lee. Hsiao and Kao were found to have lobbied other judges to secure a "not guilty" ruling for Hsiao's son. A year later, in October 2011, Lee, Shen Mei-chen, and Liu Yu-shan announced a review of the government subsidy available to farmers. The inquiry was opposed by multiple members of the Legislative Yuan, and the parliament eventually passed an amendment raising the value of the subsidy to NT$7,000. After civilians broke into a military compound in December 2011, Lee and Huang began an investigation into the Republic of China Army's security measures. In 2012, Lee and Teresa Yin moved to impeach National Taiwan University Hospital director Ko Wen-je for an oversight in organ donation and transplantation. Control Yuan President Wang Chien-shien remarked in 2013 that the agency should be abolished. Lee criticized Wang for the statement, replying that Wang did not work to improve the Control Yuan, but only attempted to limit its powers. Shortly after the April 2014 execution of Liu Yen-kuo as ordered by Justice Minister Luo Ying-shay, Lee began review of the case, as he suspected a violation of due process.