The work was also the first to make a distinction between the general principles governing administrative proceedings, and the special rules applicable to specific authorities or areas of law.

He was elected MP by the Province of Tarragona representing the Principality of Catalonia on February 23, 1810 and he assented to the first session of a Spanish parliament in its history on September 24, 1810.

He also participated in the debates on the abolition of torture, the freedom of the press, the organization of the provinces, the reform of the Treasury and the regulations of the Regency Council.

He was enthusiastic supporter of the single direct taxation, already projected by the Marquess of Ensenada, with the suppression of provincial revenues and conservation of customs and some monopolies.

After the repeal of the 1812 Constitution by King Ferdinand VII, Lázaro focused to the government of the Cervera University, continuing with its economic studies.