ERSE's Statutes are set forth in Decree-Law No. 97/2002, of 12 April (turns Entidade Reguladora do Sector Elétrico (the Electricity Sector Regulatory Authority) into Entidade Reguladora dos Serviços Energéticos (the Energy Services Regulatory Authority) and approves the respective Statutes), subsequently amended by:

• Decree-Law No. 200/2002 of 25 September (Amends Decree-Law No. 97/2002, of 12 April, which turns Entidade Reguladora do Sector Elétrico into Entidade Reguladora dos Serviços Energéticos and approves the respective Statutes)
• Decree-Law No. 212/2012, of 25 September (Introduces the 2^nd amendment to the Statutes of Entidade Reguladora dos Serviços Energéticos, transposing Directives 2009/72/EC and 2009/73/EC, of the European Parliament and of the Council, of 13 July, concerning common rules for the internal market in electricity and natural gas, respectively, and repealing Directives 2003/54/EC and 2003/55/EC of the European Parliament and of the Council, of 26 June)
• Decree-Law No. 84/2013, of 25 June (Introduces the 3^rd amendment to the Statutes of Entidade Reguladora dos Serviços Energéticos, with a view to completing the transposition of Directives 2009/72/EC and 2009/73/EC, of the European Parliament and of the Council, of 13 July 2009, concerning common rules for the internal market in electricity and natural gas, respectively, and repealing Directives 2003/54/EC and 2003/55/EC of the European Parliament and of the Council, of 26 June 2003)
• Decree-Law No. 57-A/2018, of 13 July (Amends the Statutes of Entidade Reguladora dos Serviços Energéticos, expanding regulation to the sectors of liquefied petroleum gas in all its categories, petroleum-derived fuels and biofuels)
• Decree-Law No. 76/2019, of 3 June (Amends the legal framework that governs activities related to electricity production, transportation, distribution and marketing and the organization of electricity markets)