Direitos Humanos e Direito Internacional
Core concepts
Two systems: global (ONU; Universal Declaration of 1948, ICCPR and ICESCR) and regional (OAS; American Convention of 1969 and the Inter-American Court). In Brazil, human rights treaties approved by three fifths in both houses have constitutional status (art. 5, §3); others have supralegal status (RE 466.343). Study conventionality control, the Inter-American cases on amnesty (Gomes Lund) and on contemporary slavery (Fazenda Brasil Verde), and ILO Conventions 29, 98, 100, 111, 138 and 182.
Also business and human rights: the UN Guiding Principles (protect, respect, remedy) and due diligence. Labour rights are human rights, and the social function of the company connects both fields.
Traps
A frequent trap is to treat an unapproved treaty as ordinary law: it is supralegal, above statutes but below the Constitution. Another is to confuse the Inter-American Commission with the Court, or to use the Court as a fourth instance. Also, denunciation of the American Convention is not free for states in default.
Rule of thumb
Remember the ladder: constitutional, supralegal, ordinary. Worked example: the Disability Convention (Decreto 6.949/2009) was approved under art. 5, §3, so it has constitutional status.