Of course they'll help anyone who's an irritant to us. We'd do the same in the other direction. The Chinese don't approve of sanctions in general and will try to undercut them wherever they are applied, as long as there's no risk to them.
Don't bet on there being any penalty. The Chinese did plenty of business with Saddam, with or without sanctions, and they are major players in the post-Saddam Iraqi oil industry. When money talks, memory fades. If Assad falls the Chinese will do business with whoever gets in. Of course Syria's oil exports are insignificant and the Chinese have no major vested interests in Syria, so no, the Chinese don't give a rat's ass about Assad. They'll prop him up as long as he irritates the US, when his utility is used up they'll drop him and deal with whoever gets in.
Of course that whole conversation started with the quite bizarre notion that fear of notably unspecified repercussions from China or Russia dissuaded the US from an intervention that the US never had any interest in undertaking in the first place.
Bookmarks