Isn’t that a Maxim of Law? The 6th Circuit US Court of Appeals disagrees, claiming police are exempt from both state and federal law, exempt from discovery, and exempt from Local Rules, though no judge signed the opinion in my case (many transcripts and briefs are missing from PACER, along with exhibits never sent to the appellate clerk, oral argument denied):
http://www.archive.org/details/LeeVsUsa6thCircuitUsCourtOfAppealsOpinion

Fed law ignored by 6th Circuit:

36 CFR § 4.2 State law applicable.
(a) Unless specifically addressed by regulations in this chapter, traffic and the use of vehicles within a park area are governed by State law. State law that is now or may later be in effect is adopted and made a part of the regulations
in this part.
(b) Violating a provision of State law is prohibited.

Tennessee Code �55-8-108. Authorized emergency vehicles.
(a) The driver of an authorized emergency vehicle, when responding to an emergency call, or when in the pursuit of an actual or suspected violator of the law, or when responding to but not upon returning from a fire alarm, may exercise the privileges set forth in this section, but subject to the conditions herein stated.
(c) (1) The exemptions granted under subsection (b) to a driver of an authorized emergency vehicle shall only apply when such vehicle is making use of audible and visual signals.
(Class C misdemeanor = 30 days in jail)

Wisconsin Court of Appeals opinion that police dashcam video cannot be used by the defense when it proves the defense is innocent:
http://www.thenewspaper.com/news/34/3481.asp
http://www.thenewspaper.com/rlc/docs/2011/wi-dashcam.pdf

Prosecutors Tell Cops to Lie in Trial About Breathlayzers
http://www.duiblog.com/2011/05/12/prosecutors-tell-cops-to-lie-in-trial-about-breathlayzers/