Main point of Lolita

I think the main theme of the book is how much power legal guardians have over children and how there aren't institutions to protect children from abusive parents.

A big part of this is when Humbert says "there was nowhere for her to go" after he first assaults her. He also threatens her with going to an orphanage, which according to him would be much worse, if she tells anyone about her situation. Lastly, the principal from her school doesn't at all question Humbert completely isolated Lolita. Instead of being seen as a person, she's seen as the property of her guardian