Demands that all parties to the Syrian conflict, in particular the Syrian authorities and its allies, immediately comply with their obligations under international humanitarian law and international human rights law, as applicable, including with respect to all besieged and hard-to-reach areas, calls upon all parties to implement fully and immediately all the provisions of Security Council resolutions 2139 (2014) of 22 February 2014, 2165 (2014) of 14 July 2014, 2191 (2014) of 17 December 2014, 2199 (2015) of 12 February 2015, 2254 (2015) of 18 December 2015, 2258 (2015) of 18 December 2015 and 2268 (2016) of 26 February 2016, and recalls the importance of holding accountable those responsible for all violations of international humanitarian law and all violations and abuses of international human rights law committed in the Syrian Arab Republic;