Javert also believes in facing consequences - just consequences, that match the action. He has held himself to account before. What is worrying about this situation is that he did not foresee any need for it whatsoever.

'You considered arresting me.'

It is not a question, and is delivered in a tone so hollow it practically echoes. He does not know how white he has gone, but can feel a tremor in his fingers which is not calmed by the flush of relief running through him. Relief he had no idea was necessary.

'It would not have been just.'

This comes without consideration but now it is said, he feels no need to apologise for it. It is the truth. And it is not spoken arrogantly; just a low mutter, almost to himself.