The ability of each branch to respond to the actions of the other branches is the system of checks and balances. Each branch of government can change acts of the other branches: The president can veto legislation created by Congress. He or she also nominates heads of federal agencies and high court appointees. Congress confirms or rejects the president's nominees. It can also remove the president from office in exceptional circumstances. The Justices of the Supreme Court, nominated by the president and confirmed by the Senate, can overturn unconstitutional laws.