The non-legislative powers exercised solely by the Senate are mainly those put forth in the Constitution to ensure a system of checks and balances in the Federal government, including impeachment of the president, discipline of its own members, ratification of treaties and presidential appointments. Other powers, such as declaring war, are shared by both houses of Congress.
According to the Constitution, in the impeachment of a federal official, each branch of Congress has different functions. The House of Representatives serves as prosecutor and impeaches the official, and the Senate conducts the impeachment trial. Though the president appoints people to official posts, the Senate confirms the appointments. These include members of the cabinet, judges of the Supreme Court, other federal judges, ambassadors and heads of federal agencies. The Senate ratifies treaties negotiated by the executive branch by a two-thirds vote and also can amend treaties. In the event of malfeasance in the executive branch, the Senate has the power to conduct investigations.
In the discipline of its own membership, one recourse the Senate has is expulsion, which can be accomplished by a two-thirds vote, according to the Senate website. Another disciplinary action is censure, which is a formal statement of disapproval or condemnation. In censure, a senator is not required to leave office. These actions have rarely been taken. As of June 2014, only 15 senators have been expelled, and nine have been censured.