Why is javert so intent on arresting jean valjean?

To Javert, a man obsessed with the law, to find a criminal who fools everyone, seems to rise above the law itself and command it, the idea would be maddening. On top of that, Javert and Valjean have history; Javert remembers him from the chain gang. So if someone you had once known and detested made a mockery of everything you fought to defend, you'd want to learn about them, too.