The claim: Manned internment facility - Investigating patriots were apprehended by European soldiers speaking in an unknown language. Federal government assumed custody of the persons and arranged their release.
What it really is: First let me ask, "Why would the United States be using foreign soldiers for?" That does not make any sense.
Considering how many people visit Yellowstone every year (about 3.4 million, many of them European) it would be pretty hard to keep such facility there hidden from public view.
Considering that there is no exact location of this alleged facility or details, by all appearances this story is most likely made up.