The 3-0 rejection in the case, seeking another attempt to overturn the Pennsylvania results after a lower court had tossed out the suit last week, is yet another loss in the Trump campaign’s attempt to undermine president-elect Joe Biden’s victory.
Mr Biden won the state by roughly 80,000 votes, according to Pennsylvania secretary of state’s office.
A blistering ruling from the Third District’s Stephanos Bibas – a Trump-appointed judge – said “free, fair elections are the lifeblood of our democracy”.
“Charges of unfairness are serious,” he said in his ruling on Friday. "But calling an election unfair does not make it so. Charges require specific allegations and then proof. We have neither here."
In his opinion, attached to the 21-page ruling, Judge Bibas said the Trump campaign has tried to “repackage” its claims about state law governing poll observers as “unconstitutional discrimination”.
The case suggested poll watchers did not have access to the vote-counting process, and that the state illegally allowed counties to decide whether voters could fix mail-in ballots with missing signatures or secrecy envelopes.
“Yet its allegations are vague and conclusory,” the judge said. “It never alleges that anyone treated the Trump campaign or Trump votes worse than it treated the Biden campaign or Biden votes. And federal law does not require poll watchers or specify how they may observe. It also says nothing about curing technical state-law errors in ballots. Each of these defects is fatal.”
The judge argued that the number of ballots that the campaign has targeted is far smaller than the margin of victory for it to have any meaningful impact.
“And it never claims fraud or that any votes were cast by illegal voters,” Judge Bibas said. “Plus, tossing out millions of mail-in ballots would be drastic and unprecedented, disenfranchising a huge swath of the electorate and upsetting all down-ballot races too. That remedy would be grossly disproportionate to the procedural challenges raised."
The president’s attorney Rudy Giuliani – who has repeatedly insisted that the election was marred by fraud, despite not presenting evidence in court – declared the lower-court ruling earlier this month was a victory that would bring the case closer to the US Supreme Court.
Mr Giuliani, who appeared at a hearing with GOP state lawmakers in Pennsylvania on Wednesday, intends to take the appellate court decision to the nation’s high court.
“The activist judicial machinery in Pennsylvania continues to cover up the allegations of massive fraud,” campaign attorney Jenna Ellis and Mr Giuliani said in a statement following Friday’s decision.
Those “activist” judges on the appeals court’s three-judge panel were nominated by Republicans.
“We are very thankful to have had the opportunity to present proof and the facts” to the state legislature, they said. “On to SCOTUS!”
In the lower-court ruling, US district judge Matthew Brann called the campaign’s filings a “Frankenstein’s monster” that was “haphazardly stitched together”, in his rejection of Mr Giuliani’s attempt to amend the complaint a second time. Friday’s ruling agreed with that decision.