Can I resell a video game that says "Not For Resale" on it?

Here's my dilemma: I just ordered the new Call of Duty: Modern Warfare Collection from Amazon. This includes both Call of Duty 4: Modern Warfare AND Call of Duty: Modern Warfare 2. Before I received these in the mail, I got Call of Duty 4: Modern Warfare from a friend as a gift for my birthday. I didn't want to return his gift (even though I knew I was getting the same thing in the mail), so I opened it and started playing it with him. A few days later, my order came in the mail. I just thought I would keep the one game I didn't have and resell the other game that came in the collection, but when I opened it, both of the games in the collection contained the "Not For Resale" label on the back where the barcode normally is. I was planning on selling it on Ebay, but now I'm not sure if I LEGALLY can. Can someone help me out here? I keep looking online, but cannot come up with even the slightest concrete answer. Thanks.