if they're new they will still have the factory's warrenty but make sure you make yourself some sort of receipt showing when you bought them. Usually anyone who deals with that type of ski will be able to send them back to the manufacturer for a small fee. But its worth it if you save on ebay. don't forget the receipt!
be careful. Alot of warranties are only covered from a year of purchase, if you buy from an authorized dealer. Most of the time, people selling the skis on ebay arent authorized dealers, so the manufacturer will not honor the warranty.