During the Revolution of 1848, Lalanne was briefly made head of the Ateliers Nationaux (National Workshops). He undertook a severe rationalisation of the structure set up by Émile Thomas. Brought in during May, he had closed down the institutions of the Ateliers by the end of June. In the civil unrest that occurred simultaneously he commanded a battalion of the Garde Nationale in Paris. He was detained as a subversive on 29 June, but all charges were dropped on 5 August.
