I suppose a tax loophole is nothing more then a clever application of the law, right?
So, forget about tax laws, take a simple example traffic rules.
Well, then I'm filing a patent for stopping at a red light: everyone that stops at a red light must pay me 1$.
This is exactly the same as a patent on a tax loophole: the application of laws.
You must pay the patent holder for using a specific tax loophole, which is just an application of the law.
Now I'm making you all paying for applying another law.
Patents are hilarious and disastrous.