Sessions and other Republicans on the committee are also concerned about Liu's judicial philosophy outlined in a book he co-authored, "Keeping Faith with the Constitution." In the book, Liu writes that the Constitution should be interpreted by adapting its broad principles to the conditions faced by successive generations.
The philosophy aligns him with more liberal justices on the Supreme Court, such as Justice Steven Breyer, and puts him at odds with conservatives like Justice Antonin Scalia, who as an "originalist" believes that in analyzing the constitutional text, one must give the text the meaning it had when it was adopted.
Scalia worries that those who follow Liu's philosophy will find constitutional rights that are not set forth in the Constitution.
M. Edward Whelan III, president of the Ethics and Public Policy Center, has written extensively about Liu's record on his blog in the National Review online. Of Liu's book, Whelan writes, "What Liu means by 'keeping faith' is evidently adherence to the living-constitutionalist gimmick that judges can redefine the Constitution to mean whatever they want it to mean."
"Liu has all the makings of a hard-Left judicial activist," says Whelan, "as shown by his positions on matters ranging from welfare rights to racial quotas to same-sex marriage and by his utterly lawless constitutional philosophy generally."
Jonathan Singer, a current student of Liu, disagrees. "He's someone who has an open mind, not a doctrinaire ideologue," he said.
Liu , 39, who is the son of Taiwanese immigrants , sits on the board of the liberal American Constitution Society, and opposed the nominations of both Chief Justice John G. Roberts and Justice Samuel Alito. In an op-ed, Liu wrote that the nomination of Roberts "is a seismic event that threatens to deepen the nation's red-blue divide."
In 2006, Liu testified against the nomination of Alito, saying the judge had an "exceptionally talented legal mind," but that he was concerned with "Alito's lack of skepticism toward government power that infringes on individual rights and liberties."
In 2007, Liu joined 17 other professors and submitted a friend of the court brief to the California Supreme Court, arguing that California's definition of marriage between a man and a woman violated the state constitution. The issue is likely to come before the U.S. Supreme Court in some form over the next few years.
Not all conservatives, however, are opposed to Liu. He has been supportive of charter schools and some government-funded vouchers for private schools. Such positions have earned him the praise of Clint Bolick, director of the Scharf-Norton Center at the Goldwater Institute wrote to senior members of the Judiciary Committee in support of Liu.
"I find Professor Liu to exhibit fresh, independent thinking and intellectual honesty," wrote Bolick. "He clearly possesses the scholarly credentials and experience to serve with distinction on this important court."