The Montana Code Annotated, usually cited as the MCA, is the official compilation of every permanent state law passed by the Montana Legislature, organized by subject and published for free on the Legislature’s website.1Montana Legislative Branch. Montana Code Annotated It covers criminal offenses, motor vehicle rules, taxes, property, licensing, and the rest of state law, and it is the version courts, agencies, and the public are required to use.2Montana State Legislature. Montana Code Annotated 1-11-103 – Effect of Montana Code Annotated — Official Version
How the Code Is Organized
The MCA runs from broad subjects down to individual rules through four layers. Titles are the top level and group laws by subject area. Title 45 covers Crimes; Title 61 covers Motor Vehicles.3Montana Legislature. Montana Code Annotated Title 45 – Crimes4Montana Legislature. Montana Code Annotated Title 61 – Motor Vehicles Each Title is split into Chapters that narrow the topic. Chapters are divided into Parts, which cluster closely related statutes under a shared heading. Individual laws are Sections — the smallest unit, and the piece you usually cite.
To find a law, work down the hierarchy. If your question is about motor vehicles, start at Title 61, pick the Chapter that fits your issue, then the Part, then the Section. The browse menus on the Legislature’s site follow this same structure, so the path you take through the table of contents mirrors the citation you end up with.
How to Read an MCA Citation
A citation like 45-5-201, MCA tells you three things in order: Title 45, Chapter 5, Section 201. The first number is always the Title, the second the Chapter, the third the Section. Parts don’t appear in the citation itself; they are a browsing layer, not a numbering layer.
In formal legal writing, Montana statutes are cited in Bluebook form: Mont. Code Ann. § 45-5-201 (year). The year refers to when the code volume was published, not when the law was enacted. Inside Montana courts and in everyday state practice, the shorter form, § 45-5-201, MCA, is standard.
What “Annotated” Means
Only the statutory text — the language the Legislature voted on and the Governor signed — carries the force of law. The “annotated” part refers to research material published alongside that text to help you understand and apply it. Annotations are useful, but they do not create legal obligations on their own.
The annotations typically include:
- Case notes summarizing Montana court decisions that have interpreted or applied the statute.
- Cross-references to related MCA sections or provisions of the Montana Constitution.
- Legislative history noting when the statute was first enacted and when it has been amended.
When you need to know what the law requires, read the statutory text. The annotations tell you how courts have read that text, what related provisions exist, and how the wording has shifted over time.
Where to Read the MCA
Online
The Montana Legislative Branch hosts the current MCA on its own site, and that is the version to use.5Montana Legislative Branch. Statutes From the Legislature’s homepage, the Statutes or MCA link opens the full searchable database.1Montana Legislative Branch. Montana Code Annotated You can browse by Title through the table of contents or search for specific terms. The code is updated after each legislative session to incorporate new laws, amendments, and repeals.
Third-party legal sites republish the MCA, but they can lag behind after a session closes. The state’s own site is the safest source for current law. The MCA is the only publication of the statutes that may be used in public documents, and it is treated as prima facie evidence of the law; in the rare event the printed MCA conflicts with the enrolled bill on file with the Secretary of State, the enrolled bill controls.2Montana State Legislature. Montana Code Annotated 1-11-103 – Effect of Montana Code Annotated — Official Version
Print and Older Versions
Physical copies of the MCA sit on the shelves at law libraries, many public libraries, and government offices across the state. The print set follows the same Title-Chapter-Part-Section structure as the online version. Between full reprints, print volumes are traditionally updated through pocket parts tucked into the back cover, or through supplemental softbound volumes.
If you need the statute as it read in a prior year — common in litigation, where the date of an event determines which version applies — superseded Montana statutes are available through subscription databases such as HeinOnline, which keeps historical archives for all fifty states. Some law libraries make these databases available to the public at no cost.
When New Laws Appear in the MCA
Most new Montana statutes take effect on October 1 following the session in which they passed. Appropriations bills take effect July 1. Motor vehicle tax and fee statutes take effect January 1 of the following year. Any individual bill can set a different date, and laws passed in a special session take effect immediately upon the Governor’s signature.6Montana State Legislature. Montana Code Annotated 1-2-201 – Statutes — Effective Date
The Code Commissioner handles the technical work of fitting new legislation into the existing code: placing new sections under the correct Titles and Chapters, updating cross-references, cleaning up formatting, and writing section headings that reflect each provision’s content, all without changing the meaning of the law.7Montana State Legislature. Montana Code Annotated 1-11-101 – Definitions The Commissioner can also correct spelling, grammar, and obsolete references to agency names or repealed statutes.
Statutes Are Not the Whole Picture
The MCA is not the only source of binding Montana law. State agencies adopt administrative rules under the Montana Administrative Procedure Act, and those rules carry the force of law once finalized.8Montana Secretary of State. Administrative Rulemaking Resources Statutes set the broad policy; rules fill in the operational details. An MCA section might require a license for a particular activity, while the matching rule spells out the application form, the fees, and the renewal timeline.
Rules are published separately. The Administrative Rules of Montana (ARM) is the codified collection of current rules, and the Montana Administrative Register (MAR) publishes notices when agencies propose to adopt, amend, or repeal them. Both are available at rules.mt.gov.8Montana Secretary of State. Administrative Rulemaking Resources For anything involving a regulated industry or a licensing requirement, read the ARM alongside the MCA. The statutes alone often won’t tell you everything you need to know.