Well I figure you could just ask a trainer or strength coach, they would know.
University of Nebraska was the original university to actually supply their kids with creatine, but NCAA prevents any supplying of stuff now I believe.
That being said to test for creatine would probably require a muscle sample (cutting a portion from you) lol. A urine sample would show high levels of creatinine, however it could be high for several reasons.
Don't blame me if I'm wrong, but I'm nearly sure it is legal. People have all sorts of myths about creatine. You naturally consume about 2g daily.... provided your not a vegetarian.