What resources do they have? That's such a hackneyed, easy, thoughtless, cynical cliche. Syria's oil production peaked in 1996 and as of 2011 it was below it's 1989 level. There is probably more oil in Montana shale than in all of Syria. Governments and politicians, especially in democracies, always react to public sentiment driven by news reports. There is always public pressure to "do something" whenever there is video of nerve gassing or starving children. Why else did we intervene in Somalia or in the Balkans? It certainly was not for resources.
Besides that consideration, there are very good reasons to sanction or punish the use of chemical weapons. Humanitarian reasons and the need to discourage future use of these weapons are important also and I'm sure that entered into Obama's opposition to Assad.
Syria has strategic importance being 'close to' ressources. '
One of the greatest material prizes in world history', to quote the Chief of the Division of Near Eastern Affairs in the U.S State Department, Gordon Merriam's 1945 memorandum to President Truman, and something that would lend '
substantial control of the world' according to Albert A. Berle, one of Franklin Roosevelt’s closest advisers in relation to the construction of the post-War world. The nature of US strategic interest in the region has never been a secret. Even if the US do not need the oil (and currently it doesn't), it gives great diplomatic leverage.
The stance of US policy makers on the use of chemical weapons in the Syrian conflict is an interesting one for a country with such a rich history of everything from abstaining from laws against chemical, nuclear and biological weapons (including the Geneve convention) to using chemical weapons on civilians in countries such as Vietnam and Iraq, helping wonderful allies like Saddam Hussein build up his chemical and biological weapons arsenal, to openly supporting him gassing Iranians, to the support of the close US ally; Israel, Syria's neighbour, sitting on the Middle-East's largest stockpile of chemical weapons.