By signing the Energy Community Treaty in 2005, countries in the Western Balkans, Ukraine and Moldova agreed that the European Union's competition rules are to be applied also within their territory. A number of energy sector investments are being planned that may not so far have taken adequate account of State aid rules. This briefing therefore provides a summary to draw attention to relevant requirements of EU law and highlight the risks of failure to take them into account when planning investments. The account when planning investments.