Part of that is that we're being misled by this whole 'impersonated a police officer' spin. He didn't pull the trucks over and say, "I'm a cop! You're under arr

Part of that is that we're being misled by this whole 'impersonated a police officer' spin. He didn't pull the trucks over and say, "I'm a cop! You're under arrest." Rather, he claimed (and presumably believed) that he possessed, as a highway engineer, the authority to detain trucks that were violating a statute. Consider, in carrying out his official dutues, he has some degree of discretion in doing so. For example, some engineers might decide the best tool for their job that day is a slide rule. Others might decide on a given day to use an autoleveling level. And some, particularly Mr. Large, might decide on exercising the "detain trucks that are interfering with road work" provision. It turned out there was no such provision, and Large's job didn't have the authority to detain vehicles. But the absence of a statute specifically forbidding state employees (other than police officers) to detain trucks meant that he was entitled to qualified immunity. Keep in mind that QI doesn't mean that the injured party isn't entitled to damages at all, it just means they have to sue the state and not individual officers/officials. Of course, suing the state has its own hurdles. Some government bodies have very short statutes of limitations for filing lawsuits against them, and they must receive advance notice before the claim can even commence. And the claim might need to be filed in a special court. And the state may be protected from liability if it had no advance knowledge of a condition, or by a statute limiting the amount of damages.