The Turks let the downing of their reconnaissance jet go unanswered. But the Turks have responded to a mortar attack that killed Turkish civilians with retaliatory artillery strikes (but with just 6 rounds total) and with an authorization to use force:
The Anadolu Agency says legislators on Thursday voted in favor of the bill that gives the government authority for one year to send troops or warplanes to strike Syrian targets whenever it deems it necessary.
Remember, too, that Syria threatened to use chemical weapons if invaded. Even Iran has publicly warned Assad against using chemical weapons, but Assad's position is eroding despite ramping up the killing of civilians in opposition areas (reportedly ordering his forces to kill all males between the ages of 16 and 60 in pro-rebel areas).
Turkey is also calling for NATO support.
NATO may not want to attack Assad, but if elbows keep flying at the border, Syrian actions will exceed the threshold of looking the other way and require an alliance response, notwithstanding Russia's call for NATO to stay away from Syria.
Assad can't hold the entire country. Attempting to do so in the north is just providing ample pretexts for Turkey to intervene. Assad should pull his troops back from the Turkish border.
Actually, Assad should retreat to a rump Syria of some variable dimensions, depending on what the state of his ground forces are.
And Russia has to decide whether they will continue to support Assad's control of all Syria--which Assad isn't doing now and can't accomplish the way he is doing--or support Assad in holding what he can reasonably control.
UPDATE: Interesting. Rather than being something new, the legislation is a renewal of 5-year-old authorization to strike into Syria to fight Kurdish rebels.
Which fits with this dilemma.