[3] He became a general councilor for Ille-et-Vilaine representing the canton of Cancale in 1910, and held this seat for thirty years.

He was high commissioner to the British government for regulation of allied maritime affairs from April to September 1917.

[2] On 16 November 1919 Guernier was reelected deputy and sat with the Gauche républicaine démocratique (Democratic Republican Left).

[3] He was elected chairman of the Ille-et-Vilaine council in 1921 in place of René Brice, who had died, and held the presidency until 1924.

[2] In this post Guernier said public broadcasting had to "establish across the nation a continuous spiritual connection so that alongside the grand national works that advantage Paris and our other large cities, the innumerable equally powerful and precious works generated throughout many parts of our provinces can also be diffused over the entire country.

[3] On 10 July 1940 Guernier was among the deputies of the Democratic and Radical Independent Left who voted for the constitutional change requested by Marshal Philippe Pétain that established the Vichy government.