Knowing that Russia has supplied Syria with chemical weapons in the past it is not hard to hypothesize that Russia may have been the ones who allowed Syria to use blister gas on its own people. Even though the Syrian government said they were not the ones who carried out the attack, the accounts from the victims do not match up, causing assumptions that they are lying. Syria is known to produce, store, and weponized chemical agents, so it's not a stretch to believe that Russia was the one who supplied them with the chemical procureurs for this chemical attack. Either way, based on the accounts of the victims, the Syrian government broke international law. Instead of going to war with Syria, I believe the United States need to utilize option 3. Meaning, the United States needs to team up with the UN or their allies and try to put Assad on high court. Once he is there it is highly unlikely that he will be let free. After his prosecution, the United Nations can all come to an agreement with the input of the Syrian people to give them a government that will work with and respect the people.
Although this plan would be most ideal, it is very unlikely to happen. Due to the fact that Russia is allies with Syria, it is unlikely that they will allow anything that will take Assad out of power. If Russia does agree, which is highly unlikely, it will be very hard to get Assad in a position to get him to leave. Assad controls 25% of Syria and the majority of his supporters are fanatically patriotic and would die than have him leave power. Military action wouldn't work because the countries that boarder Syria won't allow it. Iran is an ally of Syria so if a country were to invaid Iran would join the war. Also, if a country were to invaid they would not just be fighting the Syrian government. ISIS and other terrorist groups that hold control of parts of Syria will also be fighting against the invading countries. Now, if it were all to work out and Assad would be able to be procesuted, there would be a lack of power in Syria. The terrorist groups, rebels, and greedy countries will all try to gain control of the country. If there were to be a new person put in power, it is unlikely they they will be a fair leader and we risk the fact that a terrorist group could gain more power or land. If everything goes smoothly and a fair leader is put in power, oil prices will skyrocket. Now that a leader that is fair to the people and impartial to other countries is in power, the revenue coming from the oil will no longer go to the United States or any other country, meaning oil in the US will be expensive and the US will not be getting the money that is sold from Syria. Now, if everything works well and the US or other world leaders are not upset with the switch in power, there are still terrorist. The war on terror will not go away with the switch of power in Syria and terrorism might grow from the amount of foreign invasion that would have to happen in Syria. Due to all of these reasons the plan is not feasible and would be tremendously expensive. Most likely the United States will invade without the permission from the UN and will break international law causing more controversy in the world.