For obvious reasons, it is against the law for anyone to use a storage unit to keep illegal items or things that are stolen. The illegal items include any street drugs, drug making equipment, or any paraphernalia that is related to the usage of such drugs. In addition, it is usually against the rules to keep any type of firearms in a storage unit. However, there are some storage companies that may allow certain types of firearms to be stored as long as their strict firearm rules are adhered to at all times.

Items that might attract insects and vermin are not permitted to be placed in storage units. This includes all foods, fragrant items, items made from animal products, and any live plants or things made from parts of plants such as wreaths or other decorations. Of course, it is illegal to house any type of live animals in a storage unit. This is not only due to the fact that they attract vermin, but it also breaks the laws against animal cruelty.

Storing jewelry, coin collections, or other valuable items is sometimes allowed if there is proof of insurance on the specific items. This is usually up to the individual in charge of the storage facility because if the value is very high it poses a higher risk of someone breaking it to steal it.