Let's watch the Iranian worship of international law:
Iranian lawmakers and commanders issued stark warnings to the United States and its allies on Tuesday, saying any military strike on Syria would lead to a retaliatory attack on Israel fanned by “the flames of outrage.”
So let's see, if American attacks Assad's forces for using chemical weapons (Iran funny enough has experience of being gassed by a Baathist government), Iran will retaliate against a wholly uninvolved state.
No direct attack on Iran.
No UN Security Council resolution.
We'll ignore the part about how "flames of outrage" over Assad being punished for poison gas use is kind of damning of those outraged.
Of course, doesn't this give a green light to someone striking Iran for whatever reason that they choose in response?