At the start of March 1898 Guérin was among the speakers attacking Jews and their "Dreyfusard servants" at a meeting of 800 people in the Salle Wagram in Paris.

After failing to gain financial backing from Radical and Socialist politicians for his anti-Semitic league and newspaper, he turned to royalists and announced himself an opponent of the Republican government.

Guérin was financially supported by Prince Philippe, Duke of Orléans, the Orléanist claimant to the French throne, from 1898 to 1903.

Guérin refused to be taken and fortified his house in the Rue de Chabrol with a group of armed supporters.

The term Fort Chabrol for a siege situation is still in use in some French-speaking countries, even among law enforcement agencies.