## Facts

- Sugar refinery workers at Ingenio El Potrero, S.A., belonged to Section 23 of the Mexican Sugar Workers Union (STIASRM).
- The workers resigned from STIASRM and sought to form a new union.
- STIASRM invoked an exclusion-for-separation clause in an industry-wide collective instrument (contrato-ley) requiring dismissal of workers who leave the union.
- The employer dismissed the workers at the union’s request.
- A Federal Conciliation and Arbitration Board upheld the dismissals as lawful under the clause.
- A federal collegiate labor tribunal granted constitutional relief in part, finding the clause’s enforcement violated constitutional protections, while not reaching broader statutory constitutionality.
- The union sought review in the Supreme Court of Justice of the Nation (First Chamber), limited to constitutional questions.

## Issues

1. Whether statutory provisions authorizing exclusion-for-separation clauses in collective agreements and industry-wide instruments violate constitutional protections for freedom of work, association, and unionization.
2. Whether dismissing workers solely for leaving an incumbent union to form another union violates those individual constitutional rights.
3. Whether a union’s collective interest in solidarity and bargaining strength can justify job loss triggered by union disaffiliation.

## Decision

- The Supreme Court (First Chamber) upheld constitutional protection for the workers.
- The Court held that Federal Labor Law provisions authorizing exclusion-for-separation clauses (including in contrato-ley instruments) were unconstitutional insofar as they permit dismissal for leaving a union.
- The Court ruled that enforcing the exclusion-for-separation clause against workers who resigned to form a new union violated constitutional guarantees of freedom of work and freedom of association, including union freedom.
- The Court limited its holding to exclusion-for-separation and did not decide the constitutionality of exclusion-for-entry clauses.

## Legal Principles

- Freedom of work is violated when continued employment is conditioned on maintaining membership in a particular union.
- Freedom of association includes both the right to associate and the right to disassociate; legal mechanisms that penalize disaffiliation infringe this right.
- Constitutional protection of union organization is violated by rules that allow an incumbent union to trigger dismissals to prevent union pluralism and formation of alternative unions.
- Union security mechanisms cannot be enforced through dismissal when they operate by coercing union membership and suppressing workers’ constitutionally protected choices.

## Conclusion

The Supreme Court invalidated the legal authorization for exclusion-for-separation clauses used to discharge workers for resigning from a union, holding that such dismissals impermissibly condition employment on union affiliation and violate constitutional freedoms of work and association, while leaving other forms of union-security clauses for future adjudication.


Mexican Sugar Workers Union v. Hernández Rivera, Amparo Directo en Revisión 1124/2000 (S.C.J.N. 2001)