This is extremely common practice in our system. https://en.wikipedia.org/wiki/Prosecutorial_discretion

"In our system"?

As if there is a system that catches, charges, prosecutes and/or convicts everyone who breaks the law.

Kinda violates "justice is blind" trope, no?

No, it's impossible to prosecute every violation of law, and this has been true since the beginning of time.

Would you agree that each library can't have every book ever written, and do you think there is a distinction between not selecting a book and "banning" it?

Meh, "justice is stupidly aggressive" isn't an improvement.

Every organization has limited resources.

A library can't have every book in the world. This doesn't mean that not selecting a book is exactly the same as "banning" it. It does mean the issue is nuanced.