Despite his many efforts at defense in Lolita, Humbert knows he has committed some serious violations – referring to himself as a monster, a spider, a maniac, and a hound – but it is unclear whether these self-incriminations are just gestures for the reader (and jury). Humbert certainly references the ethical dilemma he is in, but it is never so great as to prevent him from perpetrating on Lolita.
He does admit that through the memoir he intends to prove that he is not a scoundrel, but he cannot resist the descriptions of his lust. He is torn between ethics and ego, law and lust. He offers many defenses for what he has done – psychological (trying to recover from losing Annabel), legal and literary (it may be illegal here and now, but look at East India, and what about Dante and Beatrice, Petrarch and Laureen?), and personal (after all Lolita was experienced and seduced me). The degree of his justification is proven here: just because he wasn't the first to get to Lolita and just because she seduced him, he says it's OK that he carries on for years as he does. Plus his whole nymphet, enchantment, demoniac theme intends to imply that he just couldn't help himself!
Humbert pays some lip-service to ethical questions, but usually goes right back to justifying his actions.
While Lolita seems able to move past what she has experienced, Humbert remains unreconciled even at the end, because he really does not acknowledge the extent of his violations.