The original issue which you quoted and addressed was :
"The Judge that ruled that the US is bound by the Geneva Convention is wrong, ........"
That is not an issue to be decided by a Judge. That issue is directly addressed by the Supremacy Clause of the Constitution.
The separate issue of "stateless non-signatories" is irrelevant since Article 4 of the Third Geneva Convention specifically extends POW rights to "Members of other militias and members of other volunteer corps, including those of organized resistance movements, belonging to a Party to the conflict and operating in or outside their own territory, even if this territory is occupied".
In other words, you do not need to be a member of the armed forces of a signatory nation to be granted POW rights under the Geneva Convention.
Article 4 of the Third Geneva Convention only requires that the combatant be a member of a group "belonging to a Party to the conflict".
As a "party to the conflict", the combatant himself or his representative has standing to bring an issue of noncompliance of the Geneva Convention himself without the need to secure the intercession of a signatory nation.
Such a combatant, however, does have to fulfill the following conditions:
(a) That of being commanded by a person responsible for his subordinates;
(b) That of having a fixed distinctive sign recognizable at a distance;
(c) That of carrying arms openly;
d) That of conducting their operations in accordance with the laws and customs of war.
The Judge is in error in his decision not because these combatants are stateless or because "the U.S. is not bound by the Geneva Convention" but because these combatants fail the requirements set forth by the Geneva that they do not impersonate civilians, that they carry arms openly and that they conduct their operations in accordance with the laws and customs of war.