"Elena Kagan's record shows that her primarily academic and political experience and her activist judicial philosophy make her inappropriate for serving on the Supreme Court," Hatch said.
Kagan was nominated by President Barack Obama to succeed retired Justice John Paul Stevens on the nine-member high court.
Hatch is a former chairman of the Senate Judiciary Committee and also opposed the confirmation of Justice Sonia Sotomayor to succeed retiring Justice David Souter. Hatch's comments appeared Monday in an opinion piece on the National Review Online, though he first said earlier this month he wouldn't support Kagan.
"After studying Elena Kagan's record ... I do not believe that she meets the standards we should require of federal judges -- especially Supreme Court justices," Hatch said. He said Kagan has never served as a judge, and "has little legal experience of any kind."
"Judges who take control of the Constitution's meaning take away the people's control over their Constitution and destroy this essential ingredient for liberty," Hatch said. "Will the Constitution control Elena Kagan, or will she try to control the Constitution?"
Kagan "has written and spoken generally about the role judges play in our system of government. In her Oxford University master's thesis, for example, Ms. Kagan wrote that 'new times and circumstances demand a different interpretation of the Constitution' and that judges may 'mold and steer the law in order to promote certain ethical values and achieve certain social ends,'" Hatch said.
He also cited Kagan's experience as dean of Harvard Law School, saying she tried to keep military recruiters off-campus despite federal law, and as an aide for President Bill Clinton, saying she played a major role in trying to defeat a congressional "partial-birth" abortion ban.