In the State of Georgia, USA, it is actually codified that campus police (read security guards, College Police, or Board of Education Police forces), Municipal police (city Police), and Sheriffs (County Police), cannot issue an arrest (aka write an actual ticket) on anyone traveling 10mph or less above the posted speed limit. This is regardless of Construction or School Zones. This is not to say that they cannot pull you over for going above the posted speed limit and performing a spot check on insurance coverage and registration/license status below this limit and issue a verbal or written warning (no penalties); but they absolutely cannot write a ticket that incurs a fine lest the Department of Public Safety penalize the municipality through fines, withdrawal of Speed Detection Privileges, or in very severe cases of repeated violations and/or demonstrated corruption Complete withdrawal of the Municipalities police force license coupled with the complete disbandment of all officers (all of this has happened to several Municipal territories). Also, more unwritten, but if an officer gives a ticket for 11mph above the limit, DPS will not impose the penalties on the municipality, however, upon taking the matter the court the judge is under obligation of precedent to dismiss the case for reasonable doubt simply because of the +/-1mph margin of error that all detection devices have to claim (usually it doesn't have to go that far and one can simply call the procecutor/solicitor's office and have the case dropped over the phone).
Also note that State Police, a division of the above mentioned Department of Public Safety, are not under any obligation to follow the 10mph buffer rule and are legally able to ticket for someone going 1mph above the limit (however given the same reasonable doubt clause that accounts for the +/-1mph, they won't ticket anyone until at least 2mph over...and even then that's only if they're having a bad day. Also, since their pay is not in any way dependent on performance guidelines or how much revenue they generate a city (only local municipalities and/or county seats generate revenue from tickets, not the state), State Patrol is more likely to be reasonable and willing to negotiate a lesser charge on scene if the driver is respectful to the officer and wasn't operating a vehicle in any dangerous manner besides speeding (and wasn't speeding too excessively(usually 20-30mph above is too excessive) without a valid reason).
Disclaimer: I am not a lawyer but I have played one several times for myself, friends, and family in traffic court against county level tickets or below. While I'm not always perfectly successful in getting dismissals, I've never completely lost, often saving them hundreds of $$ in insurance penalties and usually at worst getting reduced fines. They also don't have to shell out $300-$600 extra to a bar certified traffic lawyer to achieve same net result. If the person comes to me with a ticket issued by GSP or DPS I'll advise them to talk with an actual traffic lawyer because there are legal and political gambles involved at that level that
a lawyer would be better equipped to negotiate (Is the officer's certification up to date and active at the time of the ticket? How likely is the officer to show up at a specific venue (Generally they're more likely to blow off a Municipal Court appearance as opposed to State Court.) (one case I've successfully had dismissed was specifically because the officer failed to show)?, How closely do your or your lawyer's of choice elbows rub with the Solicitor General or the Prosecutor of the case; or how personable is (this one can dictate what kind of deals can be agreed to before even getting to court)?)