There are six law enforcement agencies at Burning Man in various quantities. I've never had a negative experience with any of them, but I don't do substances and try to avoid doing stupid stuff like speeding there.
On the other hand, I've heard horror stories that may or may not be 100% factual since those nearly always paint themselves in a good light and law enforcement in a bad light.
All I can suggest is they are just doing their jobs - if you piss them off it will go less well for you so be courteous at the very least, although obeying the law is even better.
•Federal Bureau of Land Management Rangers
•Pershing County Sheriff’s Office
•Washoe County Sheriff’s Office
•Nevada State Department of Investigations (NDI)
•Nevada State Health Division
•Nevada Highway Patrol
The most commonly encountered agency is BLM. I've met quite a few of them and they were all quite nice. These guys love Burning Man.
Pershing County is the local police for the playa. The ones I've met have been nice, but some years they are more zealous than others.
Washoe County covers the road to BM as well as Fernley and Reno. I believe some of them are sometimes hired or loaned to Pershing County for Burning Man. I don't recall ever meeting any of them.
I've never encountered any from the 3 state agencies, but one that is not listed are the Tribal Police you may encounter on 447 when driving through the Pyramid Lake Paiute Tribal Lands.
Bear in mind that any of these agencies can and does use undercover units and some of those seem more "burnery" than many burners. Additionally if you flaunt illegal stuff - don't expect them not to do their job and uphold the law (regardless of how you feel about that law).
What To Do
1. Don't speed! Speeding is the number one reason burners get pulled over. Even one mph over the limit may get you pulled over so obey the speed limits both off and on the playa.
2. Make sure all your lights are working properly, including your license plate lights.
3. If using a bicycle rack and it obscures your license plate, zip tie it to the bicycle wheel or in a visible place. At night position a flashlight to illuminate it. In recent years many burners have been getting pulled over for obstructed plates so this is important.
4. No open containers! No partying until you are parked and in your camp site.
5. Do not do substances in view of the street or on the entry / exodus lines.
6. Do not leave illegal stuff in plain sight.
7. Do not give alcohol to anyone under 21.
The following is from the Lawyers For Burners group and suggests how to handle interactions with law enforcement on the playa or when in transit.
How to Speak to Law Enforcement
Officer, my name is [give your real name].
Am I free to go?
If I am not free to go, please explain to me your probable cause for
I politely refuse to give you any further information.
I do not consent to any search of me or my belongings, tent, vehicle or
Remember that your best defense against citation or arrest may be politeness. However, nothing requires you to incriminate yourself, and an officer may cite you for revealing any illegal behavior.