Cargo should not liquidate station assets to the detriment of the station. Anything sold must be done so with thought put in to how it could negatively affect the station.
Resources in maintenance such as tools, materials, and air/water tanks are generally not of critical importance to the station. Vendors are generally considered important enough to not be sellable outside of special cases.
When there is no station emergency, cargo should generally be acquiring items to sell through the salvage department or through cooperation with other departments. Departments may surrender items that they do not need so that they can be sold, but the sale must still not be detrimental to the station. An engineer cannot normally surrender every pair of insulated gloves that the engineering department has. Certain items, like vending machines, belong to the station as a whole, and cannot be surrendered by any specific crewmember.
During a station emergency, restrictions become looser. For example, if cargo needs money to buy equipment to defend the station when there are confirmed nukies, most things can be sold without issue. Cargo would likely not be allowed to sell all the stations guns and armor, but could certainly sell vending machines and hydroponics trays.
Crewmembers can report any theft to security, and can treat theft from them or their departments as an escalation step. When escalating, players may be held liable for poor or unreasonable assumptions.
Limitations
Nothing in this clarification is intended to limit the ability of security or command to disallow sale of station property.