To be fair, Mikey, the UK did "bring him to justice" - after a fashion. He was jailed for seven years in 2006. It was our efforts to chuck him out which failed miserably until 2012 (when, of course, he should still have been in prison but for our ridiculous custody rules which sees convicts released after serving less than half their sentence).
The cause of these failures - step forward none other than the European Court of Human Rights and their determination to see his rights projected and the safety of UK citizens jeopardised. Only when the ECHR had been satisfied (and one of the stipulations they made was that, if convicted, he would not be sent to a "Supermax" prison) was he extradited to the US.
Compliance with the European Convention on Human Rights is, of course, a condition of EU membership so back we come to the old (now over ripe) chestnut. If we want the ability to chuck our people like Abu Hamza our membership of the EU must cease.