Congress has no constitutional authority to order the feeding tube re-inserted. Instead they issued legislation allowing the Schindlers to file a de novo review of the merits of the case, and for the Court to grant all declaratory and injunctive relief as necessary to protect the rights of Terri Schiavo.
That's why DeLay et al were so sure the feeding tube would be re-inserted on Sunday. In order to have a de novo review of the merits of the case, Terri Schiavo would need to be alive and thus the injunctive relief sought re-inserting the feeding tube should have been granted by Whittemore.
However, Whittemore screwed up by applying the civil procedure standard for injunctive relief by saying the Schindlers would not prevail on the merits. But IMHO, that's not the standard Congress authorized for granting injunctive relief. The standard was all releif necessary to protect the constitutional rights of Terri Schiavo. Congress required Whittemore to issue the injunction to re-insert the feeding tube so there could be a trial on the merits.
I agree the law passed by Congress could have used some work but there are grounds for a successful appeal here.
"After a determination of the merits of a suit brought under this Act, the District Court shall issue such declaratory and injunctive relief as may be necessary to protect the rights of Theresa Marie Schiavo under the Constitution and laws of the United States relating to the withholding or withdrawal of food, fluids, or medical treatment necessary to sustain her life.
It seems to me that Congress is giving the Court the leeway to determine the merits of the suit. And I suspect that it couldn't be otherwise. Congress cannot simply order a Court to issue a particular ruling.