In most jurisdictions, some loopholes are legal to exploit while others aren't. Loopholes in tax laws are legal to exploit because it is not criminal to try and minimize your taxes. However, gaining unauthorized access to a system is criminal so exploiting loopholes is not legal. I think using loop holes in tax law should count as tax avoidance, but it currently doesn't.

During the Nuremberg trials the Nazis that stood accused actually unsuccessfully tried to exploit what was essentially loop holes in international law.