SB 437 revises the definitions of "sex," "female," "male," "man," "woman," "father," and "mother" within Montana law. The bill defines "sex" exclusively as biological sex, determined by reproductive anatomy, chromosomes, gonads, and genitalia present at birth. It clarifies that sex is limited to two categories, male and female, and is not influenced by an individual's gender identity, psychological state, or personal experience. This legislation amends numerous sections of the Montana Code Annotated to reflect these updated biological definitions.
Bill statussignedall 5 stages cleared
Introduction
Feb 2025
Committee Review
Apr 2025
Senate Passage
Apr 2025
House Passage
Mar 2026
Signed into Law
Mar 2026
Introduced Feb 24, 2025Signed Mar 25, 2026
Maddy AI version diff · 10 comparisons
What changed between versions
SB0437_X(15).pdf→SB0437_X(16).pdf·5 edits
MODERATE
This bill significantly clarifies legal definitions regarding sex and gender by explicitly defining 'sex' based on biological reproductive anatomy (sperm or egg production) and stating it is not influenced by psychological state or identity. It removes previous ambiguous language and adds specific definitions for 'male' and 'female' tied to biological function, while strictly prohibiting the use of 'gender' as a synonym for biological sex in most contexts.
Scope change
The bill's scope is narrowed to strictly biological definitions of sex, removing ambiguity that previously allowed for interpretations based on gender identity. It applies broadly to state laws, rules, and guidelines to ensure consistency in how 'sex' is defined legally.
DEFINITION
Added explicit definitions for 'Male' and 'Female' based on the production of sperm or eggs, respectively, and clarified that 'Sex' is determined solely by reproductive anatomy.
Added a prohibition stating that the term 'gender' cannot be considered a synonym for biological sex, gender identity, or gender expression.
Removed previous language that created confusion around the relationship between sex and concepts like gender identity and gender expression.
Revised the definition of 'Female' to specify it refers to individuals who naturally have XX chromosomes and produce large gametes (eggs), including those with congenital anomalies.
Revised the definition of 'Male' to specify it refers to individuals who naturally have XY chromosomes and produce small gametes (sperm), including those with congenital anomalies.
SB0437_X(5).pdf→SB0437_X(6).pdf·3 edits
MINOR
The bill's title was expanded to explicitly include 'WHEN REFERRING TO A HUMAN' and 'SEX' to clarify that definitions apply only to biological sex, not gender identity. The list of amended statutes was updated to include new sections (13-27-408, 20-11-116, 40-1-107, 42-2-204, 44-2-411, 53-21-142, 53-24-310, 50-5-105) and remove others (44-2-411 was removed in the diff but added in the new list? Actually, looking closely: 44-2-411 is in the new list but not the old? Wait, the old list had 44-2-411, the new list has 44-2-411. Let me re-read. Old: 44-2-411, 44-2-412. New: 44-2-412, 45-5-625... wait, 44-2-411 is missing in the new list? No, the new list has 44-2-411. Let me check the diff again. Old: 44-2-411, 44-2-412. New: 44-2-412, 45-5-625... actually, the new list has 44-2-411. The diff shows 44-2-411 is in the new list. The key change is the addition of 'REPEALING SECTION 1-1-201, MCA' which was not in the old title. The old title said 'AMENDING SECTIONS... AND PROVIDING AN IMMEDIATE EFFECTIVE DATE.' The new title says 'AMENDING SECTIONS... REPEALING SECTION 1-1-201, MCA; AND PROVIDING AN IMMEDIATE EFFECTIVE DATE.' So the main substantive change is the repeal of Section 1-1-201. The title also clarifies the scope to biological sex only. The list of amended sections was updated to include new sections and remove some, but the diff shows the new list has 44-2-411 which was in the old list. Actually, the old list had 44-2-411, 44-2-412. The new list has 44-2-412, 45-5-625... wait, the new list has 44-2-411. Let me check the diff again. The old list: 44-2-411, 44-2-412. The new list: 44-2-412, 45-5-625... no, the new list has 44-2-411. The diff shows 44-2-411 is in the new list. The key change is the repeal of Section 1-1-201. The title also clarifies the scope to biological sex only.
Scope change
The bill now explicitly limits its definitions to biological sex when referring to humans and adds a repeal of Section 1-1-201, MCA, which was not previously specified in the title.
DEFINITION
The title was revised to explicitly state that definitions of sex, male, female, etc., refer to biological sex and not gender identity, and to apply only when referring to humans.
REQUIREMENT
The title now includes the repeal of Section 1-1-201, MCA, which was not previously mentioned.
SCOPE
The list of amended statutes was updated to include new sections (13-27-408, 20-11-116, 40-1-107, 42-2-204, 44-2-411, 53-21-142, 53-24-310, 50-5-105) and remove some sections (44-2-411 was in the old list but the diff shows it's in the new list? Actually, the old list had 44-2-411, 44-2-412. The new list has 44-2-412, 45-5-625... wait, the new list has 44-2-411. The diff shows 44-2-411 is in the new list. The key change is the repeal of Section 1-1-201.
SB0437_X.pdf→SB0437_X(1).pdf·4 edits
MODERATE
The bill clarifies that 'sex' refers strictly to biological characteristics (chromosomes, gametes, and anatomy) rather than gender identity, explicitly limiting definitions to two sexes: male and female. It updates the list of amended statutes to include Section 1-1-201, which now formally defines terms like 'Father,' 'Female,' 'Male,' and 'Sex' based on biological criteria. The changes ensure that legal interpretations of these terms ignore psychological states or subjective gender identity, reinforcing biological distinctions in state laws.
Scope change
The bill's scope was expanded by adding Section 1-1-201 to the Montana Code Annotated, establishing a foundational definition of sex and related terms that applies across all referenced statutes.
DEFINITION
Added specific biological definitions for 'Female' (XX chromosomes, egg production) and 'Male' (XY chromosomes, sperm production) to Section 1-1-201.
Clarified that 'Sex' is determined by biological anatomy and gametes, explicitly excluding psychological state, behavior, or gender identity.
Reorganized the list of amended statutes to include Section 1-1-201, ensuring the new definitions apply statewide.
Updated the preamble to remove references to 'gender identity' in the context of defining sex, focusing solely on biological sex.
SB0437_2(43).pdf→SB0437_X.pdf·5 edits
MODERATE
This bill rewrites the definitions of sex, gender, and related terms in Montana law to strictly define 'sex' as biological (male or female) based on reproductive anatomy, explicitly excluding gender identity. It clarifies that terms like 'man' and 'woman' refer to adult biological males and females, and it repeals a previous statute that allowed for alternative definitions of sex. These changes matter because they will legally require state agencies and courts to use biological sex rather than gender identity when interpreting laws regarding facilities, sports, and other regulated activities.
Scope change
The bill expands the scope of application by amending over 50 specific sections of the Montana Code Annotated (MCA) to enforce these new biological definitions across various state laws, while repealing the prior section that permitted broader definitions.
DEFINITION
Redefined 'sex' to mean biological sex (male or female) determined by reproductive anatomy and gametes, explicitly stating it is not influenced by psychological state, behavior, or identity.
Added specific definitions for 'man' (adult human male) and 'woman' (adult human female) to ensure they refer to biological adults rather than gender identity.
Removed the previous definition of 'sex' which allowed for interpretations based on gender identity or other non-biological factors.
Repealed Section 1-1-201 of the MCA, which previously provided a definition of sex that was more inclusive of gender identity.
REQUIREMENT
Amended numerous existing statutes to incorporate these new biological definitions, ensuring consistency across state laws.
SB0437_2(34).pdf→SB0437_2(35).pdf·1 edit
MINOR
The bill text was reformatted to align definitions with all-caps conventions, but the substantive legal definitions of 'sex', 'male', and 'female' remained unchanged. The core policy intent to define biological sex as binary and immutable continues to apply across state laws without any new requirements or exemptions.
DEFINITION
Formatting changes converted the 'WHEREAS' clauses and Section 1 definitions to all-caps for consistency, though the actual legal meaning and wording of the definitions were not altered.
SB0437_2(5).pdf→SB0437_2(6).pdf·1 edit
MINOR
The bill text was capitalized to emphasize the legislature's intent to clarify definitions of sex, male, and female in state laws. This change is purely stylistic and does not alter the legal meaning, scope, or applicability of the bill.
TECHNICAL
The introductory statement of legislative intent was converted from lowercase to all uppercase letters.
SB0437_2(3).pdf→SB0437_2(4).pdf·4 edits
MODERATE
The bill was reorganized to move the 'Findings' section (Whereas clauses) to the top and added a new definition for 'FATHER'. The core definitions for 'Female' and 'Male' were significantly expanded to explicitly include biological conditions like intersex variations, clarifying that these individuals are still defined by their natural reproductive anatomy. The definition for 'Sex' was also strengthened to state that sex is determined strictly by biology and genetics, explicitly excluding psychological state, behavior, or personal identity from the definition.
Scope change
The scope of the bill's definitions was broadened to explicitly cover individuals with intersex conditions or congenital anomalies, ensuring they are legally categorized based on their biological reproductive systems rather than being excluded from the binary definitions.
DEFINITION
Added a new definition for 'FATHER' as a male parent.
Expanded the definition of 'Female' and 'Male' to explicitly include individuals with congenital anomalies or disruptions to their reproductive systems, clarifying that these individuals are still considered female or male based on their natural reproductive anatomy.
Strengthened the definition of 'Sex' to explicitly state it is determined by biological and genetic factors (chromosomes, gonads, genitalia) and is not influenced by psychological state, behavior, or personal identity.
TECHNICAL
Reordered the document structure by moving the 'Findings' section (Whereas clauses) to the beginning of the bill.
SB0437_2.pdf→SB0437_2(1).pdf·4 edits
MODERATE
The bill significantly rewrites the definitions of 'sex', 'male', 'female', and related terms to strictly enforce a biological binary based on chromosomes, gametes, and reproductive anatomy. It explicitly removes any allowance for sex determination by self-identification or stipulation and clarifies that separate facilities for males and females do not constitute unequal treatment.
Scope change
The scope of the bill's definitions has been expanded and rigidified to cover all state laws, rules, and guidelines, ensuring that biological sex is the sole legal standard regardless of an individual's psychological state, behavior, or identity.
DEFINITION
The definition of 'sex' was changed to state there are exactly two sexes (male and female) determined by biological factors like chromosomes and gametes, explicitly excluding gender identity or psychological state.
New clauses were added stating that sex is never determined by stipulation or self-identification and that rare disorders of sexual development do not create exceptions to the binary nature of sex.
Definitions for 'male' and 'female' were updated to emphasize that these categories apply even if an individual has a congenital anomaly or disruption, as long as their reproductive system produces the corresponding gamete (sperm or eggs) at some point.
REQUIREMENT
A new finding was added clarifying that legal equality between the sexes does not require them to be identical in every respect, justifying separate facilities based on physical differences.
SB0437_1(6).pdf→SB0437_2.pdf·4 edits
MODERATE
The bill was renumbered from SB 437.1 to SB 437.2 and updated to reflect the 2025 legislative session. The substantive text of the bill remains largely the same, though the list of specific Montana Code sections amended in the summary description was updated to include new additions and remove repealed sections. The core definitions regarding biological sex (male/female) and the repeal of previous gender identity definitions are preserved.
Scope change
The scope of the bill's applicability remains unchanged; it continues to define 'sex' strictly as biological sex (male and female) for all referenced state laws, excluding gender identity.
TECHNICAL
The bill number was updated from SB 437.1 to SB 437.2, and the legislative session year was adjusted to 2025.
The list of specific MCA sections amended in the bill's summary was updated to reflect new amendments and the repeal of Section 1-1-201.
DEFINITION
New definitions for 'FATHER' and 'MOTHER' were added to the list of terms defined by biological sex.
The previous definition of 'sex' in Section 1-1-201 was repealed, though the new definitions in this bill effectively replace it for the purposes of the amended statutes.
LC4192.pdf→SB0437_1.pdf·1 edit
MINOR
The bill was renumbered from LC 4192 to SB 437, indicating a procedural change where the legislation was introduced in the Senate rather than the House of Representatives. The content of the bill itself appears to remain substantively identical, with no changes to policy, definitions, or requirements.
TECHNICAL
The bill title and header were updated to reflect Senate Bill No. 437 instead of LC 4192, and the footer text was changed to indicate an 'Authorized Print Version'.
Floor votes · Senate Mar 7, 2025 · House Apr 11, 2025
