Granted this is a long ass read, but the attorney raises a good question, considering it's untested law.
Based on the way the law is written, you could literally murder someone on federal land in Idaho and there's really no direct line in the law connecting it to Idaho, Wyoming or federal law for prosecution.
I've no doubt the current Congress or even SCOTUS would create a work around (stretch, think John Roberts) to usurp the Constitution, making it a retroactive law (Also illegal) just to close the loophole after the fact.
But it's interesting to know that someone knew enough about the law to spot this obvious black eye. If I ever need a lawyer, I'm looking this guy up!
The Perfect Crime
Brian C. Kalt
Georgetown Law Journal, Vol. 93, No. 2, 2005
MSU Legal Studies Research Paper No. 02-14
This article argues that there is a 50-square-mile swath of Idaho in which one can commit felonies with impunity. This is because of the intersection of a poorly drafted statute with a clear but neglected constitutional provision: the Sixth Amendment's Vicinage Clause. Although lesser criminal charges and civil liability still loom, the remaining possibility of criminals going free over a needless technical failure by Congress is difficult to stomach. No criminal defendant has ever broached the subject, let alone faced the numerous (though unconvincing) counterarguments. This shows that vicinage is not taken seriously by lawyers or judges. Still, Congress should close the Idaho loophole, not pretend it does not exist.
Kalt, Brian C., The Perfect Crime (2005). MSU Legal Studies Research Paper No. 02-14. Available at SSRN: https://ssrn.com/abstract=691642