INTRODUCTION:
Health regulation is a fundamental instrument for guiding priorities and strategies, especially in crisis contexts. The COVID-19 pandemic tested the resilience of health systems, requiring rapid responses to ensure access. This study investigated the role of regulation in access to health services, focusing on emergency care networks in two distinct contexts: the state of São Paulo (Brazil) and Portugal.

METHODS:
A multiple-case study with a qualitative approach was conducted. Data collection took place in 2022 through five regional workshops in São Paulo (involving 99 managers and professionals) and 14 individual interviews with experts and decision-makers in Portugal. A semi-structured script was used, focusing on four dimensions: policy, structure, organization, and lessons learned. Data underwent thematic analysis to identify units of meaning related to regulation and access.

RESULTS:
In Portugal, regulation was centralized, with strong coordination between the Ministry of Health and technical institutions (DGS, INFARMED), facilitating uniform national protocols. In São Paulo, the absence of federal coordination led to the strengthening of regional and municipal regulation, notably the CROSS system for bed management. Both systems adapted infrastructure and care flows (such as SNS24 in Portugal and triage units in SP). Common challenges included human resource shortages and the need for extraordinary funding, addressed through emergency decrees.

CONCLUSIONS:
Regulation proved to be a vital articulating element for maintaining access during the pandemic. While Portugal benefited from a centralized and cohesive structure, São Paulo highlighted the importance of regional resilience in the face of central governance gaps. Strengthening regional regulation and integrating information systems are crucial lessons for increasing the robustness of health systems in future global emergencies.