Unlawful combatants do not qualify for prisoner of war status. Their situation upon capture by the enemy is covered by the Fourth (Civilian) Geneva Convention if they fulfil the nationality criteria and by the relevant provisions of the Additional Protocol I, if ratified by the detaining power.
This protection is not the same as that afforded to lawful combatants. To the contrary, persons protected by the Fourth Convention and the relevant provisions of Protocol I may be prosecuted under domestic law for directly participating in hostilities. They may be interned for as long as they pose a serious security threat, and, while in detention, may under specific conditions be denied certain privileges under the Fourth Geneva Convention. They may also be prosecuted for war crimes and other crimes and sentenced to terms exceeding the length of the conflict, including the range of penalties provided for under domestic law.
Persons not covered by either the Third or the Fourth Geneva Convention in international armed conflict are entitled to the fundamental guarantees provided for by customary international law (as reflected in Article 75 of Additional Protocol I), as well as by applicable domestic and human rights law. All these legal sources provide for rights of detainees in relation to treatment, conditions and due process of law.
Therefore, contrary to some assertions, the ICRC has never stated that all persons who have taken part in hostilities in an international armed conflict are entitled to prisoner of war status.