In 650, Wei Siqian accused the powerful
chancellor Chu Suiliang of forcing a government interpreter to sell his land to Chu. Initially, the deputy chief judge of the supreme court, Zhang Ruice (), ruled that Chu had broken no laws because he had paid compensation to the interpreter, but Wei pointed out to
Emperor Gaozong that Chu had paid just the amount of compensation equal to government
condemnation of the property, not fair market value, and Emperor Gaozong demoted Chu to the post of prefect of Tong Prefecture (同州, roughly modern
Weinan,
Shaanxi). However, Emperor Gaozong respected Chu and recalled him to be a chancellor again in 652, after which Wei could not be promoted and was at one point demoted to the post of magistrate of Qingshui County (清水, in modern
Tianshui,
Gansu). Despite this, however, he commented: At one point, the official Huangfu Gongyi () became the secretary general for Emperor Gaozong's son
Li Xian the Prince of Pei, and he invited Wei to serve as Li Xian's treasurer. He stated to Wei, "You, sir, are not just a small fish in the pond, but I would like to ask you to serve for a few years to watch out for the foundation of this princely mansion." Eventually, he was promoted to be a secretary at the executive bureau of government (尚書省,
Shangshu Sheng). Early in Emperor Gaozong's
Yongchun era (682–683), Wei served as
Shangshu Zuo Cheng (), one of the two secretaries general of the executive bureau, and then as imperial censor. At that time, the general Tian Renhui () had a dispute with Wei's subordinate Zhang Renyi () and falsely accused Zhang of crimes. Emperor Gaozong personally interrogated Zhang, and Zhang, fearful of the emperor, was unable to respond coherently. Wei instead spoke: Wei's subsequent defense of Zhang was eloquent, and Emperor Gaozong was impressed. While he served as censor, he would not bow to princes or dukes, and when some people pointed out that this might bring him trouble, he stated: "Eagles [(often used as a symbol of censors to show that their functions are to look out for illegalities)] are not friends of all birds. Why should I bow to them to ingratiate them? Further, officials who serve as ears and eyes of the emperor should be independent of others." == During Empress Dowager Wu's regency ==