Usenet is completely legal and has been around since before there was even an internet for Universities to communicate.
Of course, sharing illegal files can breach the copyright laws of many countries and we won’t pretend that this isn’t rife on Usenet. But, simply having a Usenet account is not a crime and many old-school computer enthusiasts use it for nostalgia and legit research.
In recent years less copyright material has been appearing on Usenet due to tougher enforcement of laws and cross-country approaches.
Most pirated material has come from Usenet servers hosted in the Netherlands where file-sharing is a legal gray area.