This book seeks to address the phenomenon of whistleblowing in the light of European court decisions. It also provides an in-depth study of comparative law, the legal systems of which can be used to compare the Portuguese General Whistleblower Protection Regime. As can be seen, the Portuguese legislator took advantage of the fact that the European Whistleblowing Directive is a minimum harmonisation directive to give Law 93/2021 a broader scope than that required by European standards.