[gamblor956]

None of these tax "planning" schemes are available anymore.

Moreover, tax authorities have increasingly taken the position that the use of these planning methods constitutes tax evasion. The Dutch Sandwich and Double Irish were grandfathered in (meaning, not treated as criminal tax evasion) but a company utilizing similar schemes today would ultimately result in one or more of their executives spending time in jail.

Critically, most of tax law is actually regulation that implements statutes. Tax planning schemes that satisfy the technical letter of regulations but which violate the plain intent of the written statute can, and have, been deemed illegal years or even decades later (see, for example, the Bermudan tax loss harvesting scheme), and this has repeatedly passed constitutional muster.