" The passing of sentences must also be pronounced by a regularly constituted court, affording all the judicial guarantees which are recognised as indispensable by civilised peoples. "
for international:
"It also specifies that when there is any doubt whether a combatant belongs to the categories in article 4, they should be treated as such until their status has been determined by a competent tribunal."
>None of the Geneva Conventions actually say this.
One way or the other it is mentioned in various places through the Conventions. In particular http://en.wikipedia.org/wiki/Third_Geneva_Convention :
for internal conflict
" The passing of sentences must also be pronounced by a regularly constituted court, affording all the judicial guarantees which are recognised as indispensable by civilised peoples. "
for international:
"It also specifies that when there is any doubt whether a combatant belongs to the categories in article 4, they should be treated as such until their status has been determined by a competent tribunal."