According to what I understand, the United States copyright law says downloading for free, the pdf version of a copyrighted book that you don’t own, even for personal use, is illegal. Does this make it assur l’halacha because of Dina d’malchusa? And would it make a difference if I would have never have paid money for the book anyways, and I’m not causing a loss to the copyright owner?
Let’s look at each point individually.
If copying someone else’s work is stealing, the fact that would not have bought it anyways will not permit copying it. First of all because it is still stealing. Secondly, people tend not to want to buy things because they can always get it for free. Therefore the fact that people say that wouldn’t have bought it is not always correct.
Regarding your other point, dina d’malchusa dina will only apply if indeed the United States enforces the copyright laws. However if it is an official law, but the government doesn’t care about it or enforce it, it would not be included in dina dmalchusa dina.