The Constitution (Article I, section 5, clause 2 ) empowers the Senate to set its rules. Senators have used that power over time in different ways. As a result, a complex assortment of standing rules, statutory rules, standing orders, and precedents presently regulate how the Senate makes decisions.
The Senate has forty-four standing rules . They specify things like the oath of office that the vice president administers to new senators (Rule III), the committees to which the Senate refers draft bills (Rule XVII), and the process to end floor debate/filibusters (Rule XXII). The Senate’s standing rules are general and do not address circumstances that frequently arise in specific debates. They total seventy pages.
Unlike in the House, senators do not have to approve standing rules at the beginning of every Congress. This is because the Senate is a continuing body. Only one-third of its seats are up for grabs every two years. Consequently, the Senate’s standing rules remain in effect from one Congress to the next until senators change them (Rule V) or choose not to follow them.
Statutory rules also regulate Senate debates. Senators create them by adding rule provisions to bills that the president signs into law. For example, the Congressional Budget Act of 1974 (Public Law 93-344 ) established the rules that govern Senate debates on budget resolutions and reconciliation bills. And the Omnibus Budget Reconciliation Act of 1990 (Public Law 101-508 ) made the 1986 Byrd-Rule prohibition on non-budgetary/extraneous provisions in reconciliation bills permanent.
Statutory rules also expedite the consideration of trade agreements. For example, the Bipartisan Congressional Trade Priorities and Accountability Act of 2015 (Public Law 114-26 ) reauthorized Trade Promotion Authority (TPA). TPA established special fast-track procedures in the Senate (and House) by which Congress considers trade agreements submitted by the president. Amendments are precluded, and debate time is limited.
Like the standing rules and statutory rules, standing orders also regulate how the Senate operates. Standing orders may be either permanent or temporary. Senators establish permanent standing orders by passing a simple resolution. Permanent standing orders remain in effect until senators repeal them if an expiration date is not otherwise noted in the text of the order itself. The Senate Manual  lists standing orders currently in effect under the heading, “Nonstatutory Standing Orders Not Embraced In The Rules, And Resolutions Affecting The Business Of The Senate.” Examples of permanent standing orders include the requirement (almost always ignored) that senators vote from their desks and radio/television coverage of the Senate’s proceedings.
In contrast to permanent standing orders, senators utilize temporary standing orders on a routine basis in the form of unanimous consent agreements. The rules established in this way remain in effect only for the period specified in the agreement. They are listed in the Congressional Record  on the day they are adopted. For example, the Senate approves several temporary standing orders by unanimous consent at the beginning of each Congress that remain in effect for that Congress’s duration. These include agreements to set aside a limited period each day for the majority and minority leaders’ use. Senators also use temporary standing orders to schedule floor speeches, amendment debates, and votes.
Senators may look to precedent to determine how best to regulate their debates whenever the standing rules, statutory rules, and/or standing orders fail to address specific parliamentary situations. The Senate’s Chief Clerk, William J. McDonald, compiled the first collection of precedents (A Compilation of Questions of Order and Decisions Thereon)  in 1881. McDonald organized the precedents alphabetically by topic. (Topics included things like offering amendments, debating bills, and voting.) It was only 25 pages long.
The clerk of the Senate Committee on Privileges and Elections, George P. Ferber, compiled a 350-page collection of precedents in 1893 (Precedents Related to the Privileges of the Senate.) In 1894, the clerk of the Committee to Investigate Attempts at Bribery, etc., Henry H. Smith, expanded Ferber’s work to 975 pages in a new collection that also included some House precedents (Digest of Decisions and Precedents of the Senate and House of Representatives of the United States).
In 1908, the Senate’s chief clerk, Henry H. Gilfry, compiled a user-friendly collection of precedents (Precedents: Decisions on Points of Order with Phraseology in the United States Senate) that totaled approximately 700 pages. Like McDonald’s 1881 collection, Gilfry organized Precedents alphabetically and by topic. He updated it in 1914, 1915, and 1919 to include new precedents that were not in earlier versions.
In 1954, Senate Parliamentarian Charles L. Watkins and Assistant Parliamentarian Floyd M. Riddick prepared the first edition of the collection (Senate Procedure: Precedents and Practice) that senators still use. The parliamentarian’s office updated the collection in 1964, 1974, and 1981. Alan Frumin compiled the precedents for the collection’s current edition (Riddick’s Senate Procedure) in 1992. It totals more than 1,600 pages.
The Senate sets a precedent when its presiding officer rules on points of order against rule violations. And the Senate sets a precedent whenever a senator successfully appeals the presiding officer’s ruling on the point of order. The presiding officer’s response to parliamentary inquiries may also set a precedent. Although senators generally consider responses to parliamentary inquiries non-binding, a response may gain precedential value over time to the extent that it provides future Senates with insight into past parliamentary practice.
Senate debates are regulated by a complex assortment of standing rules, statutory rules, standing orders, and precedents. The Senate’s rules and practices can contradict one another (i.e., a statutory rule may contradict a standing rule; a precedent may contradict a standing rule). In such instances, the last rule or practice agreed to by the Senate is operative. This is because standing rules, statutory rules, standing orders, and precedents all have the same effect on how the Senate operates. They are binding only to the extent that senators agree to follow them.
- “Article I, section 5, clause 2”: https://www.archives.gov/founding-docs/constitution-transcript#toc-section-5-
- “forty-four standing rules”: https://www.rules.senate.gov/rules-of-the-senate
- “Public Law 93-344”: https://www.congress.gov/93/statute/STATUTE-88/STATUTE-88-Pg297.pdf
- “Public Law 101-508”: https://www.congress.gov/101/statute/STATUTE-104/STATUTE-104-Pg1388.pdf
- “Public Law 114-26”: https://www.congress.gov/114/plaws/publ26/PLAW-114publ26.pdf
- “Senate Manual”: https://www.govinfo.gov/content/pkg/SMAN-116/pdf/SMAN-116.pdf
- “Congressional Record”: https://www.congress.gov/congressional-record
- “A Compilation of Questions of Order and Decisions Thereon)”: https://www.legislativeprocedure.com/s/MacDonald-Precedents-pkhr.pdf