"Our government is supposed to be based on 'checks and balances' e.g. the president's veto, Congress' override of a veto, impeachment etc. What are the checks on Supreme Court justices, who are appointed for life?" — Robert B. Steup, Middleburg, Fla.
There are two types of powers the other two branches hold in "checking" and "balancing" the Supreme Court: the power to appoint and impeach Supreme Court justices and the ability to write and amend laws.
The Constitution grants the president the power to appoint district and appellate court judges, including the Supreme Court justices, by and with the "advice and consent" of the Senate.
While it has been the tradition of the Senate to confirm most Presidential appointees, there have been several cases of stalemate and even dismissal, including the rejection of President Reagan's appointment of Robert Bork in 1987 and the refusal of the Senate to act on many of George W. Bush's appellate and district court nominees.
The legislative branch also has the power to impeach justices: The House officially charges the judge and the Senate holds the trial.
http://www.congress.org/news/2010/07/19/what_checks_the_supreme_court