"There is no way in heck any reasonable federal judge would let this stand, for the simple reason that states may not vote away their sovereignty. Or really, the sovereignty of their citizens."
That isn't what they are doing. The legislature is simply saying any federally badged sworn law enforcement agent is also to have State level law enforcement authority in this State as well. There actually isn't anything that says a federal agent not a resident of Colorado, for that matter even a foreign national, cannot have law enforcement authority in Colorado.
In fact, New Mexico a few years back was looking at letting Mexican nationals be State law enforcement agents. Matt Bracken even wrote such a thing in his book Domestic Enemies just weeks before the public disclosure of New Mexico's desire to do so.
This is a hole in our constitutions where no one would even think such as person could have any authority.
The New Mexico idea was not challenged in federal court, and especially since Clarence Thomas “breathed life” into the Privileges or Immunities clause, I doubly think it would not fly now, despite what state legislators might think.
Importantly, note the repeated mention of *just* the Secret Service, as if they are the only federal police that matter.
The authority of the Secret Service is very precisely delineated in the law. Enforcement of local and state laws that are not federal felonies is not within their authority.
If a federal agent exceeds his delegated authority and commits a tort (civil wrong) within a state, he may be sued in state court; see Johnston v. Earle, 245 F. 2d 793 (9th Cir. 1957); and Hunsucker v. Phinney, 497 F. 2d 29 (5th Cir. 1974). A state cannot excuse him of this offense, by offering to extend his authority, because they cannot do this in federal law.