//Could MPs block an EU exit if Britain votes for it?//
The answer is that technically MPs could block an EU exit - but it would be seen as political suicide to go against the will of the people as expressed in a referendum. The referendum result is not legally binding - Parliament still has to pass the laws that will get Britain out of the 28 nation bloc, starting with the repeal of the 1972 European Communities Act.
One scenario that could see the referendum result overturned, is if MPs forced a general election and a party campaigned on a promise to keep Britain in the EU, got elected and then claimed that the election mandate topped the referendum one. Two thirds of MPs would have to vote for a general election to be held before the next scheduled one in 2020.//
Source - there is more.
http://www.bbc.co.uk/news/uk-politics-32810887