The Book Thief might challenge our ideas about crime and criminality. What if the laws of the land require its citizens to commit crimes against humanity? That's what's going on in Nazi Germany during most of the novel. Our main characters decide to err on the side of kindness and love, regardless of what the laws say. Liesel's stealing of books and her and Rudy's other adventures in thievery could be seen as symbolic of the way everything is topsy-turvy in this society. One must steal and break the law in order to maintain a basic positive humanity. These courageous characters risk everything, day and day again, to resist unjust laws.
The Book Thief does a good job of showing how laws can be used to commit crimes.
Liesel's book stealing is justified because she uses the books to help herself and others.