How has the EU misused their power?
1. Common Agricultural Policy inefficient use of EU money. Subsidies given for political reasons rather than economic. Cost of CAP was over 60% of total EU budget, this has now fallen to 45%
2. Bureaucracy. Costs of bureaucracy of EU are a high % of total expenditure
3. Common Fisheries Policy. This is estimated to cost at least £1 billion a year to Britain in lost jobs and reduced catches. But, has also failed to stem over fishing in the north sea. 
4. Over Regulation - It is estimated that 70% of new British laws come from Brussels. Holland claimed that enforcing EU regulations has led to a cost equal to 2% of GDP.
 Report is by Bruges group which is anti european. Statistics can be manipulated. For example, the Bruges group claim the cost per head of EU membership is £873, but, according to Foreign and Commonwealth office the cost is about £300 per head  (and this is before the benefits of membership are included.
 To answer the question has the EU misused its power may require a consideration of political factors, such as loss of local democracy. However, the impact of the political nature of the EU, is not in the remit of Economics
See also: Benefits and disadvantages of EU membership