Syrian rebel groups are more or less in unanimous agreement about not liking ISIS, and excluding them from both the ceasefire and peace talks was pretty uncontroversial. The question of al-Qaeda’s affiliate, Jabhat al-Nusra, is another matter entirely.
The Nusra Front has been used as a front-line fighting forces in the Syrian rebellion for years, and has close alliances with several “moderate” rebel factions. Though it’s unthinkable in practice to allow al-Qaeda into the peace process, let alone to be part of the post-war government, many rebel groups feel clearly beholden to them.
Other factions, however, aren’t so sold on Nusra, believing the group’s ideology makes it unsuitable for postwar Syria, and its involvement in the war little more than a temporary convenience. Some are openly talking about the post-war unity army being able to wipe out Nusra in short order.
That may prove overly optimistic, however, with the Nusra question splitting the rebels heavily, and getting seriously in the way of the peace talks, as many don’t want to negotiate a settlement that will ultimately cut their al-Qaeda allies out of the picture, and even if they do end up making a deal, expelling al-Qaeda from its territory is going to e no small task.