That would not be the smart thing to do. Sanctions would hurt EU economy more.

There are a lot better responses: reduce copyright length, to let's say... 50 years? Make everything after 1976 public domain. EU economy could even get a boost from that.

Or, if EU wanted to keep this limited to justice, denounce extradition treaties for all but most serious crimes (expecially not allowing any future Assange to be extradited), repeal laws that forbid bypassing DRM protections and reverse engineering.