I don't think there is a justification for big corporations to do what they do and they have to be pursued. I've been working for a bank in a tax haven in Europe and I've seen that financial engineering powerful people use has been a known and accepted tool for the governments for a while, and now that Europe is living a financial crisis governments start asking. These companies play in an absolutely different league…
26 U.S. Code § 7201 - Attempt to evade or defeat tax:
"Any person who willfully attempts in any manner to evade or defeat any tax imposed by this title or the payment thereof shall, in addition to other penalties provided by law"
I have worked at companies performing the "double-irish". True, they aren't prosecuted. But legal? Because a british lawyer says it is? 26 U.S. Code § 7201 is extremely easy to read and meant to be very vague. It isn't complicated. They "could be viewed as" breaking the US law and that is enough for some IRS investigators. Why they don't? Further: https://upload.wikimedia.org/wikipedia/commons/c/c3/Double_I...
The above info graphic clearly shows an attempt to defeat the US the 26 U.S. Code § 7201. This is not only illegal but morally reprehensible.