Towing Issues: Towing illegally parked vehicles from Apartment Complex, property owner associations, parking violation sticker

Question
I manage a 12 unit apartment complex in Santa Cruz, CA. Years ago I applied with a towing company, ( I think) about towing illegally parked cars on the property. I seem to recall that I filled out some forms and then had a sign posted with a "CV" something and CHP phone number. At any rate, recently I left a "Warning Parking Violation" sticker on a tenant's illegally parked car.  The tenant said that had talked with the local Sheriff and he said that the sticker was illegal and threatening to tow was illegal.  I spoke with a Sgt. at the local Sheriff's office and he said because it was private property the sticker was totally legal and if they didn't move their vehicle, tow it away.
My question is what should I do as far as paper work and/or where do I look to ascertain the law regarding towing illegal vehicles from an apartment complex?

Answer
California has been tackling the towing issue on both state and local levels for some time now.  

Laws which were current and applied 1 year ago are now changed to new laws.  

Best thing to do is contact a company which does tow aways, and see if they can provide you with information regarding the laws.  I also think that you might get some help from any landlord - property owner associations regarding the laws.  I try to keep up with the laws in california (I am in Alabama) and there are always new ones referenced on both state and local levels.  Way to many to actually keep track of ...

Notice that the vehicle is about to be towed is seen to many as illegal, but it does also provide the required notices to the vehicle owners under some laws.

Signs at the entrances to the complex also sometimes meet the requirements.  

If you have both then it should be legal.   I am sure that you as a property manager have seen most every excuse or reason for things. I think the person is trying to blow smoke somewhere ...

Check out the city laws if you can, and county laws also. State laws are great to have on hand also.  If I was a manager of the property and parking was a big issue then I would have a 3 ring binder of the applicable laws on hand in the office in case you need to take some actions.  Never hurts to have information before acting .