I'm guessing you probably live in an apartment complex. There is this scam going on in the greater Denver area that is actually legal. Towing companies contact the managers of apartment communities and offer to provide "parking enforcement services" for FREE to prevent persons other than tenants from parking in the lots. Once a contract is signed, all the law requires them to do is post a sign warning that "unauthorized vehicles will be towed at owner's expense" with a contact number, then they can impound any vehicle that violates the rules stipulated in the contract.

Common violations include: expired registration sticker, expired temp tag, missing plate, "for sale" sign, commercial vehicle, flat tire, leaking oil or fluids, appears inoperable, appears to be used for storage, improperly parked.

If your vehicle is in "violation" they can tow and impound it, and if you cannot pay the impound fee they can keep or and resell it. If they saw a motorcycle with no tags and a for sale sign they would steal it -- legally. If you show up while they are about to remove it they will require you to pay a $70 "drop fee" in order to give you a warning and leave . . . but then they can show up an hour later and try taking it again. If you try to stop them, Colorado law is on their side since the management company has given them authorization to remove vehicles and they have the same authority as a security guard regarding confrontations and use of force.

It is a reprehensible practice, and as far as I know unique to the Denver area -- at least in the overall scope of its enforcement.