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Subsidiarity as a legal and political principle of European law was introduced by the Maastricht Treaty in 1992. Since that time it has caused heated discussion about its relevancy and importance in the constitutional order of the European Union. Subsidiarity is a concept signifying that decisions should be made as closely as possible to the citizens. Study will focus on the main problems about the delimitation of spheres of subsidiarity application and its task in defining the level of exercising the power. In addition, as subsidiarity is included in the body of EC Treaty, the jurisdiction of the European Court of Justice covers the justiciability of the principle. Study presents several cases where the Court developed the approach towards possible claims on violation of subsidiarity. The principle is rather flexible and triggers new improvements in the decision-making process of the European Community bodies.

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Mariya Pereginets was born in 1980 in Ternopil, Ukraine. 1997- 2002 graduated from Kyiv Mohyla Academy , law, and then got LLM in Comparative Constitutional law from Central European University,Budapest. Now she works as lawyer. In 2005 Mariya was the coauthor of the book Legal regulation of the customer protection in EU and Ukraine .

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