An EU body with legal personality established by Regulation 713/2009, which has since been recast by Regulation (EU) 2019/942. ACER provides a framework within which the national energy regulators of EU member states can co-operate. At its inception, its role was mainly advisory, but its role has grown. It has powers to adopt individual regulatory decisions in specific cross-border situations, as well as decisions on certain technical matters, and market monitoring roles. It has a key role in relation to the adoption of the EU network codes for gas and electricity. ACER commenced operation on 3 March 2011 and is based in Ljubljana, Slovenia. For more information, see Practice notes: