This is getting off-topic, but as a Northern European I'm constantly dumbfounded by the proliferation of police--and even worse, paramilitary--organizations in the US, both public and private. Around here, even privatized parking enforcement (on private parking zones) is a hotly contested issue and private parties issuing parking "tickets" is currently illegal.

Well, for most situations here, it's because City/State police are underfunded and understaffed and cannot meet the needs of a small city like a University in a timely manor. The law enforcement officers for a University typically train the same as city police and abide by the same/similar governing regulations.

For a campus that may have 30,000-50,000 people on it at any given time, you do need to be able to have quick responses when an incident does occur. The campus police at my local university actually do more than a typical police department might -- sending out txt messages to all students when there is an incident or threat, update details frequently, Help Call Boxes in the parking lot for at night, etc. They even handle situations when a student pulls the alarm during finals week (something that an outside police department would not be able to rapidly respond to and would get annoyed with quickly).

Some universities even have their own fire departments. Most have medical staff on duty for students as well. Some even have dentists and optometrists, etc. They really are "small cities".

To be honest the idea of having a police department / legal force on campus is crazy, but I understand why it is happening.

Just wondering though you do sign an agreement with the campus that they are allowed to, right?

Depends on the size of the campus. I went to a school that was about 4 square miles and had upwards of 50,000 people there every day. Lower Manhattan is about the same size, though it does have many, many more residents. 50k is a good sized town. It's a little weird, but not unreasonable.

At least at University of Wisconsin campuses there's a good legal reason for a campus to have its own police: city and county police by default don't have jurisdiction within state agencies like the University.

So, thus they have their ow departments, like police.

Meh, they learned it from us Northern Europeans... http://en.wikipedia.org/wiki/Oxford_University_Police

anyone can make an arrest, but campus police et al can't shoot you legally as the government police can, they can't call in other branches of government like swat or air support or even the military, they can't take you to jail, after an arrest they need to call the real police. There's a big difference between campus police which are benign and the regular government police. sometimes (as at UC Davis) the campus police get ahead of themselves and start acting like the real police, but thankfully they can be reigned in, unlike the real cops who can do whatever they want and get away with it.

You hinted at the UCD pepper spray incident (which was under orders of the school chancellor, but nobody remembers that and she still has her job).

The campus police can and will shoot you. They are a real-deal police department. Most of the university shootings are ended by campus police (usually shooting the gunman).

However you sort of hinted at the fact that most campus police are a lot more lenient than city/state police. This is true in my experience -- guessing, but probably because they know who they are largely working with. Students. Drunk students, students doing dumb things, etc. Not hardened criminals most of the time. I'd probably step to far, but I'd wager campus police is a much safer line of work for an officer as well (no flip of the coin if the guy you pulled over for speeding will pull a gun on you, etc).

UC Davis is a state school. State schools tend to have real police, I don't know of any private university that does (why or how would they?)

Many do. Penn definitely does, for one (http://www.publicsafety.upenn.edu/UPPD/).

Generally, you will find that the difference in 'demeanor' for campus police is due to the flow of money. For city, county, and state police... fines and fees generally flow back to their respective coffers. Campus police (technically state agencies) on the other hand (generally) have budgets appropriated by the state regardless of revenue generation. This is why you will often hear stories of a drunken college student being escorted home instead of arrested; there is no financial interest in having them arrested.

Edits: grammar

This is not true. I know the University Police at my college are full fledged state police officers and have all the same rights, protections, and duties as a city patrol officer.

To give one random example, University of Washington police are King County Sheriff deputies with a different shoulder patch. They have the same abilities as our local transit police and the handful of towns that contract to KCSO for their local policing.

The UCPD are technically State Police and are definitely real cops that can arrest and/or shoot you.