Peel have been deducted six points and fined by the Isle of Man Football Association.
The penalty is for playing new signing Terry Rigaux at the start of the current season while he was suspended.
He moved to the island in the summer and was still under suspension from his time at previous club Burtonwood Albion, who play in the Warrington and District League.
A statement from Peel says they will "vigorously" appeal the sentence and will refer the matter to the English F.A..
Peel slip to third in the Sure Mobile Premier League 13 points behind leaders Rushen but with two games in hand.
In Combination One, St. George's have been docked 12 points for fielding two ineligible players. They drop from second place, and just a point behind leaders Old Boys, to fifth in the table.