"The Senate's presiding officer typically does not have responsibility for proactively ensuring that matters under consideration comply with the rules. Instead, Senators may enforce the Senate's legislative rules and precedents by making points of order whenever they believe that one of those rules or precedents is, or is about to be, violated. Under some circumstances, a ruling by the presiding officer determines whether or not the point of order is well taken. Under others, the Senate itself decides the point of order, usually by majority vote. Senate Rule XX states in part that '[a] question of order may be raised at any stage of the proceedings, except when the Senate is voting or ascertaining the presence of a quorum, and, unless submitted to the Senate, shall be decided by the Presiding Officer without debate, subject to an appeal to the Senate.'"
CRS Report for Congress, 98-306
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html