The judicial Power of the United States, shall be vested in one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish.
I am not entirely sure that the bill explicitly involves Terri Schiavo anyway, but rather applies to all such cases. I don't have the bill text handy, though.
The Schiavo threads on here are getting downright nasty. Just a word of warning. I'll try and get that bill text.
The Courts get their power from Congress.