Sams ressurection.

Hey folks, I was just wondering if someone could clear something up for me.

Now I could have totally got this wrong but I thought I'd just ask anyway. I vaguely remember back in season 4 when Dean was brought back from the dead, Ruby told Sam something along the lines of "No demon can swing that". As in, no demon can bring back the dead.

Now, Crowley is saying he brought back both grandfather Sam and our Sammy. But Crowley is a demon? I mean I know he was then "The king of hell", but he was still a demon. He diddn't exactly get special powers that we know of cause he was killed so easily. I dunno, it just doesn't sit right with me. I just think if it is a mistake, its a bit of a careless one. Even if Crowley could suddenly bring back the dead, it just seems a little lame. I dunno, don't hate me! I just wanna know if I'm completely wrong or not lol.