Jones v. Clinton, 520 U.S. 681 (1997), was a landmark United States Supreme Court case establishing that a sitting President of the United States has no immunity from civil law litigation against him, for acts done before taking office and unrelated to the office.
The Wikipedia entry on the legal case of Clinton v. Jones explains.
On April 12, 1999, Wright found Clinton in contempt of court for “intentionally false” testimony in Jones v. Clinton, fined him $90,000, and referred the case to the Arkansas Supreme Court’s Committee on Professional Conduct, as Clinton still possessed a law license in Arkansas.
The Arkansas Supreme Court suspended Clinton’s Arkansas law license in April 2000. On January 19, 2001, Clinton agreed to a five-year suspension and a $25,000 fine in order to avoid disbarment and to end the investigation of Independent Counsel Robert Ray (Starr’s successor). On October 1, 2001, Clinton’s U.S. Supreme Court law license was suspended, with 40 days to contest his disbarment. On November 9, 2001, the last day for Clinton to contest the disbarment, he opted to resign from the Supreme Court Bar, surrendering his license, rather than facing penalties related to disbarment.