On the most basic level, civilians are protected by the same general humanitarian principles that govern the treatment of POWs, the wounded, and others not taking an active role in the conflict. Any form of physical violence or degradation is prohibited. An armed force may not attack civilians, nor use them as a "human shield" to render a location protected from attack.
The general purpose of the fourth Geneva Convention is to shield civilians, and children in particular, from the effects of war. It provides for "neutralized zones" where fighting is prohibited, and hospital and safety zones for the protection of the sick, the elderly, pregnant women, children under 15 and mothers of children under seven. These zones are supposed to be labeled with a huge Red Cross sign to ensure their protection. Children are supposed to wear identity badges in case they are lost or orphaned. Hospital workers are also supposed to carry special identity cards so that they are never prevented from performing their duties.
Enemy forces are not allowed to seize personal property unless it is being used against them, and in that case, they must return the property or provide compensation at the end of the war. The main exception to this rule occurs in the case of occupation, when all property related to news reporting may be seized, but even then, the occupying force must return the property or pay for it at the end of occupation. Every building or object connected to religion, charity, education, the arts and sciences and history is protected by the laws regarding private property, even when it is state property.
According to Hague law:
Territory is considered occupied when it is actually placed under the authority of the hostile army. The occupation extends only to the territory where such authority has been established and can be exercised.
In other words, an armed force is considered in charge if it is, in fact, in charge. Once the occupying force can no longer control the territory, it is no longer an occupying force and is once again simply "the enemy." An occupying force has the absolute responsibility of providing for the basic needs of the people under its control, including food, clothing, shelter, medical attention, and the maintenance of law and order. An occupying force cannot just sit by as occupied territories are looted -- in almost all cases, the laws that were in place in the territory before occupation are still in place after occupation. It is only the enforcer that has changed.
An occupying force cannot punish civilians for anything that occurred before occupation, including anything they may have said against the country now in charge.
Even (or especially) in the case of occupation, communication between civilians, in particular between family members, is treated as an basic right. It may be curtailed only if the correspondence is deemed detrimental to the safety of the occupying force, but even then, civilians may communicate using special forms that allow for at least 25 "freely chosen words" (Geneva IV).
Civilians must not be interned or removed to another country unless it is for their own safety or the safety of the state, and only if there is no other alternative. If people are transferred from an occupied territory, it can only be to another country that has signed the Geneva Conventions. In the case of either internment or transfer, it must be temporary, and the occupying force must make all necessary arrangements to keep track of the people, keep families together and return them to their homes at the end of the hostilities. Occupying forces may not import their own citizens into the occupied territory.
It is legal to force civilians to work, but not in a military capacity against their own country and not as slave labor -- they must be paid for their work. If civilians are used to police a work camp, they cannot be forced to physically punish other workers. International organizations like the Red Cross must have access to civilians at all times and must have access to all work camps, internment camps and "assigned residences." An occupying force is not allowed to tattoo civilians as a means of identifying them.