THE CONSTITUTIONAL SHIELD AGAINST FORMALISM: OBJECTIVE GOOD FAITH AS A LIMIT TO CONTRACTUAL ABUSE IN HEALTH PLANS (CASE ANALYSIS 2024/2025)

Abstract

This scientific article analyzes the imperative observance of objective good faith (Article 422, Civil Code) and the duty of loyalty in supplementary health contractual relations, under the perspective of the social function of the contract (Article 421, Civil Code) and the horizontal efficacy of fundamental rights, notably the right to health and the dignity of the human person. The study demonstrates that the essential nature of the health contract mandates a reinterpretation of Contract Law, thereby limiting the private autonomy of health plan operators. Objective good faith is examined in its integrating functions (creation of ancillary duties, such as informing and cooperating) and, above all, its limiting function (abuse control), acting as a protective shield against the disproportionate exercise of rights. The research focuses on recent jurisprudence (2024/2025) of the Superior Court of Justice (STJ), which utilizes the principle to curb abusive practices, such as the unilateral termination of collective contracts for users undergoing vital medical treatment (venire contra factum proprium) and the lack of transparency in readjustments due to claim rates (sinistralidade). It is concluded that the application of this principled triad is crucial to guaranteeing fair and egalitarian access to health, transforming the contractual bond into an instrument for the materialization of human dignity and mitigating contractual formalism in the face of constitutional values.