When the laws stop protecting innocents, innocents must be protected by other means.
As a matter of principle, the administration of justice is properly the matter of the civil authorities (see Romans 13). Even if the government is in the hands of wicked people, the subjects of that government should not usurp its power. In I Samuel 24, we note that David did not kill King Saul when he had the opportunity to do so. The powers of government are rightly restricted, and when its commands are in conflict with God's Word, we are justified to disobey immoral orders of the government. However, this does not extend to a person unlawfully doing what the government should do.