This is a false alarm. Thomas for SCOTUS made a sound decision here using constitutional reasoning as the basis. Would that more decisions were made with such constitutional basis.
The Fourth Amendment protects against UNREASONABLE searches and seizures. Thomas is saying that regardless of the unreasonable stop, the police had a duty to arrest the guy based on an outstanding warrant which adds up to a reasonable search incident to the arrest.
IOW, the search as a result of the unconstitutional stop would have been disallowed.
But once it was discovered there was an outstanding warrant for this guy’s arrest, the search that followed the legal arrest was a “search incident to arrest”, perfectly OK.
That seems like a reasonable conclusion.
Sometimes it helps who is for and who is against. Thomas usually hits the nail on the head and the Ginsburg, Sotomayor, and Kagan dissent gives the decision more credibility IMO.
The stop was based on a anonymous tip at a house. Utah conceded it was a illegal stop. The person was detained merely from exiting a house that was rumored to have drugs at. Would we have put up with this coming from our British overlords; no.
So, in essence the ends justify the means.