Up to 380,000 barrels of crude oil were previously produced by wells around the city of Raqqa and in the desert region to its east that are now in rebel hands - in particular Jabhat al-Nusra, the al-Qaeda off-shoot which is the strongest faction in this part of the country.
Now the violently anti-Western jihadist group, which has been steadily extending its control in the region, is selling the crude oil to local entrepreneurs, who use home-made refineries to produce low-grade petrol and other fuels for Syrians facing acute shortages.
"Rightful liberty is unobstructed action according to our will within limits drawn around us by the equal rights of others. I do not add 'within the limits of the law' because law is often but the tyrant's will, and always so when it violates the rights of the individual." Thomas Jefferson