Constitutional Foundations of Private Autonomy: Dignity, Freedom, and the Limits of State Power in the Democratic Order

Abstract

The article demonstrates that, in the post-1988 context, private autonomy is reconstructed as a relational fundamental right: it remains a condition of freedom, but its legitimacy depends on its compatibility with human dignity, substantive equality, and solidarity. Methodologically, it employs a theoretical-dogmatic approach with hermeneutical and comparative elements (German framework), as well as an analysis of paradigmatic precedents from the Brazilian Supreme Federal Court (STF) and the Superior Court of Justice (STJ) (such as same-sex unions, supplementary health, and informational self-determination/LGPD). The results reveal:(i) the constitutionalization of private law (social function, good faith, abuse of rights); (ii) the prevalence of indirect horizontal effect, coupled with duties of protection and structured balancing; and (iii) contemporary challenges in digital contexts, including mass contracts, information asymmetries, and algorithmic regulation. The contribution lies in offering operational criteria for resolving collisions between autonomy and other fundamental rights (proportionality analysis, design of remedies, and safeguards of autonomy against paternalism). Conclusion: the autonomy protected by the legal system is a responsible autonomy, guided by Kantian parameters of dignity and non-instrumentalization, capable of balancing individual freedom and communal responsibility in unequal and digital societies.