Applicable law in Syrian conflict
The nature of Syrian conflict has been describes as a non international armed conflicts should be governed by international humanitarian law as well as the international human rights law
All the laws state the illegality of the use of torture , as in the customary norms of international human rights law :
V. Treatment of Civilians and Persons Hors de Combat
Chapter 32 Fundamental guarantees
Rule 90 Torture, cruel or inhuman treatment and outrages upon personal dignity, in particular humiliating and degrading treatment, are prohibited.
Rule 91 Corporal punishment is prohibited.
Chapter 37 Persons Deprived of Their Liberty
Rule 118 Persons deprived of their liberty must be provided with adequate food, water, clothing, shelter and medical attention.
Rule 119 Women who are deprived of their liberty must be held in quarters separate from those of men, except where families are accommodated as family units, and must be under the immediate supervision of women.
Rule 120 Accommodation for Children Deprived of Their Liberty
Rule 120 Children who are deprived of their liberty must be held in quarters separate from those of adults, except where families are accommodated as family units.
And also the Rome Statute in Article VII: Torture is a crime against humanity in Article VIII considered a war crime.