The EU is historically influenced by "virtuous" countries, which have little interest in signing bad laws; "bad" countries benefit as a result. The European Parliament, with its proportional representation system and loose alliances, can often be more easily influenced on big, visible issues, than the hardcore-conservative first-past-post Westminster (where party loyalty is paramount).

The EU is not perfect (the Commission in particular is the root of a lot of "evil" activity), but if you believe in checks and balances, it's yet another power you can appeal to when things look dire on the home front.