Legal Certainty and Legitimate Expectations in Brazilian Law

Introduction

Legal certainty (segurança jurídica) is a fundamental principle of Brazilian constitutional law, recognized as an implicit foundation of the Democratic State of Law. It encompasses the stability, predictability, and reliability of the legal system, ensuring that individuals can order their affairs based on clear and stable legal norms. The principle has been developed by the STF, particularly in cases involving changes in constitutional interpretation, tax legislation, and administrative acts.

Constitutional Foundations

Express Provisions

While legal certainty is not enumerated as an express fundamental right, it derives from several constitutional provisions: (i) the Democratic State of Law (Article 1); (ii) due process (Article 5, LIV); (iii) protection of acquired rights (direito adquirido), res judicata (coisa julgada), and the completed act (ato jurídico perfeito) (Article 5, XXXVI); (iv) non-retroactivity (Article 5, XL); and (v) prior notice for tax laws (Article 150, III, b).

Dimensions

Legal certainty has both objective and subjective dimensions:

• Objective: The legal system must be stable, clear, and predictable
• Subjective: Individuals have a legitimate expectation that the legal framework will not be arbitrarily changed

Acquired Rights, Res Judicata, and Completed Acts

Acquired Rights (Direito Adquirido)

An acquired right is one that has been definitively incorporated into a person’s legal patrimony under a prior law and cannot be affected by subsequent legislation. The STF has held that acquired rights protect: (i) rights that have already been exercised; (ii) rights whose exercise depends only on the will of the holder; and (iii) legal effects that have already occurred.

Res Judicata (Coisa Julgada)

Res judicata is the final and unappealable judicial decision, which cannot be modified by subsequent court decisions or legislation. The principle is central to legal certainty in the judicial sphere.

Completed Acts (Ato Jurídico Perfeito)

A completed act is one that has been performed in accordance with the law in force at the time of performance. Subsequent legal changes do not affect its validity.

Legal Certainty in Tax Law

Prior Notice (Anterioridade)

The tax law principle of prior notice (anterioridade) requires that a law imposing or increasing a tax must be published before the beginning of the following fiscal year (Article 150, III, b). This ensures taxpayers have sufficient time to adjust their affairs.

Novelty (Noventena)

The ninety-day rule (anterioridade nonagesimal) requires a 90-day waiting period between publication of a tax law and its effectiveness (Article 150, III, c).

Modulation of Effects

The STF may modulate the temporal effects (modulação de efeitos) of its decisions, limiting retroactivity to protect legal certainty. Under Law 9.868/1999 (Article 27), the STF may, by a two-thirds majority, restrict the effects of a declaration of unconstitutionality to protect legal certainty or exceptional public interest.

Legitimate Expectations

Concept

Legitimate expectations (expectativas legítimas) arise from the behavior of the state that creates reasonable reliance on the continuance of a legal framework. The protection of legitimate expectations is a corollary of the principle of objective good faith applied to public administration.

Application

The STF has protected legitimate expectations in cases involving: (i) changes in constitutional interpretation that affect settled expectations; (ii) administrative practices that create reasonable reliance; and (iii) transitional situations requiring protection for persons who have relied on existing rules.

Legal Certainty and Constitutional Change

Constitutional Amendments

The Constitution provides for amendments (Article 60) but protects certain matters from amendment (cláusulas pétreas), ensuring the stability of the constitutional framework.

Judicial Precedent

The CPC/2015 strengthened the role of precedent in ensuring legal certainty. The binding precedent (súmula vinculante) and repetitive appeals (recursos repetitivos) systems aim to ensure uniform interpretation and reduce judicial uncertainty.

Criticism and Balancing

Certainty vs. Justice

The principle of legal certainty may conflict with the demands of substantive justice. Rigid application of precedent or acquired rights may perpetuate injustice. Brazilian law balances these values by: (i) allowing modulation of effects; (ii) permitting retrospective application of criminal law that benefits the accused; and (iii) recognizing exceptional circumstances justifying departure from precedent.

Conclusion

Legal certainty is a foundational principle of Brazilian constitutional law, essential to the Democratic State of Law. The protection of acquired rights, res judicata, and completed acts, combined with the principles of non-retroactivity and prior notice, provides a robust framework for legal stability. The STF’s practice of modulating the effects of its decisions demonstrates an institutional commitment to balancing constitutional interpretation with the protection of legitimate expectations.