"You will not be allowed to enter the stadiums during UEFA Euro-2016 with your cockerel Balthazar," European football's governing body wrote in a letter to Tomaszewski.
"As nice as it is, the presence of your cockerel would put you in an awkward position vis-a-vis the security teams," explained the official letter, read out to AFP by a very annoyed tone by Tomaszewski on Thursday.
He is warned that he will be thrown out if he is found breaching the stadium ban on live animals.
"I am 68-years-old, this is my sixth and last Euros," he said.
Tomaszewski and his unusual pet gained worldwide attention at the 1998 World Cup in France, becoming a kind of mascot for the French team.
France fan Clement d'Antibes with his rooster 'Coq' Balthazar RT pic.twitter.com/hHk1PvXEVs— RAFIKI™ (@da_CHE_GUEVARA) June 16, 2014
"I am very upset," said Tomaszewski, recalling that he was a guest of honour at the recent inauguration of the FIFA museum in Zurich.
There was even a portrait of him and Balthazar among an exhibition of 24 footballing personalities, he said proudly.
He insisted that he wouldn't go to a match without his rooster, starting with the tournament's opening game, France v Romania, on June 10th in Paris.
"Balthazar will be there during all the Euro matches. If he isn't allowed in then I won't go in either," insisted Tomaszewski, who has tickets for all the matches France may play in right up to the final.
The Algerian-born Frenchman, nicknamed Clement d'Antibes after the southeastern coastal town where he lived, and his mascot have already been kicked out of some stadiums abroad, as well as from hotels where Balthazar's habit of crowing earlier than a lot of alarm clocks went off is not always appreciated.