Originally Posted by yarghble
I'm assuming you refrigerate your kegs? That should take care of the problem for you.
Unfortunately this is not completely correct. It will slow but not stop fermentation. The best route from what I've read is to use both cam tabs and the potassium sorbate.
Or less accurately, you could cold crash, rack to secondary sit for a month, cold crash and rack to keg for a year before back sweetening to hope that all the yeast died off during that time... I only mention it because I had a cider I did like this and it worked. But it was also more of an apple wine so there was more alcohol to help kill off the yeast.