That same year, he entered the importing business with a partner; after that business failed the following year, he returned to the practice of law.
In 1820, he was elected to the Legislative Assembly of Lower Canada for Dorchester; he represented the riding until his death at Quebec from cholera in 1832.
During his time in the assembly, he supported the Parti canadien.
In 1830, he introduced a bill incorporating the city of Quebec.
His uncle Étienne-Claude Lagueux also served in the legislative assembly.