I'm pretty sure it can. Yes it is legal, but because it has ephedrine in it I've read that it is possible to test positive for amphetamines. Your best bet is to warn them before hand and if you test positive they can do a more expensive and accurate test to show what you really took.
I checked with Cytodyne Tecnologies--the makers of Xenadrine--and yes it may show up in a standard drug test as amphetamines but if use is discontinued within 5-7 days should be out of your system.