As Wayne says I'd be very careful trying to remove it. It's obviously an after market jobby and looks to be slightly wonky(?), depending on what was used to bond it to the car paint could be damaged when you try and take it off.
That said I think that the spoilers tend to snap more often than paint gets damaged so you might be ok, use a hairdryer (a heat gun may be too hot), and some warm water. Also some nylon or even dental floss can be good to help