Is it ever morally permissible to break the law?

While Socrates, MLK, and Gandhi all held non violent views, but they seem to differ when it comes to the issue of whether or not one should ever knowingly break the law. In Platos Crito,one of the reasons Socrates gives for not escaping from prison is that it would be a violation of the laws of Athens. Socrates seems to be unwilling to break the laws of his homeland, while both Gandhi and MLK violated the law on numerous occasions during their struggles for civil rights.
So who is right? Is it ever morally permissible to break the law? Can we break a law if we feel that it is unjust? Also, how do you think that Socrates would respond to the many acts of civil disobedience during the American (or the Indian) Civil Rights Movement? Your paper should
address these questions. Be sure to provide support for your responses.