Tom Holsinger originally left this as a comment in Dan's article about the PFLP's activities in Iraq. I thought to was interesting enough to deserve its own post.
We have a simple and effective, but slow, means of terminating Syria's Baathist regime if we want to. The time required might make it costly in terms of Syrian countermeasures.
We can close Syrian and Lebanese ports with naval mines, i.e. blockade the Syrian economy, including its criminal one. The Turks like the Syrians less than we do so they'd deny use of their ports and rail lines to make up for the closure of Syrian-controlled ports. Syria's rail connections with Jordan and Saudi Arabia lack sufficient capacity to carry the tonnage necessary to keep the Syrian economy going. Ditto for all possible truck and air traffic. Even Syria's feeble economy relies on railroads from ports to carry most of the goods it requires.
The major problem with this, besides the fact that governments don't think that way these days, is the political & diplomatic problems from blockading Lebanon, which happens to be Syria's wholly controlled subsidiary.
Few understand, though, how important sea traffic through Lebanon is for the drug trade carried on by the gangster confederacy called the Syrian government aka its Baathist regime.
Cutting off that route would cause an immediate massive dive in their income while they establish new routes through Turkey for their high value, low bulk, exports. And having to share with their new Turkish cutouts would cut their profit margins.
Smuggling through Lebanon is a critical source of income for Syrian's ruling gangsters. It pays for much of their regime protective forces. A temporary shutoff of that income, and a longer-term reduction in their profit, would likely bring about regime collapse faster than the slower economic collapse.
The real drawback here, IMO, is that there might not be a replacement regime, i.e., 1980's Lebanese type chaos, for a while. Syria's Alawite minority (Shiite-related - about 10% of the population) has been dominant for many years (the Assad clan are Alawites) and is violently unpopular. There is a fair chance of it suffering genocidal massacre and ethnic cleansing at the hands of the Sunni majority when the Alawites lose power.
IMO the major reason for American caution in dealing with Syria is not difficulty in inducing regime change, but whether the consequences might be worse for some time, i.e., chaos with Islamic terrorist controlled sanctuaries in some parts of the country, and eventual emergence of a truly nutball Islamic regime. Much of this is really just fear of the unknown, but we would be taking a significant chance.
So put Bashir Assad (or Syria's Baathist gangster confederacy) in the place of Blazing Saddles black sheriff Cleavon Little, in the immortal scene from Mel Brooks' movie where he holds a gun to his own head and shouts:
"Don't shoot or I'll shoot the nigger!"