On 27 January 1796, he was elected as a member of the National Assembly of the Batavian Republic, representing the electoral district of Amsterdam IV.

[3] On 15 March 1796, he proposed an amendment to a motion regarding the takeover of the old chancery of the States General, seeking to implement cost-cutting measures and to prevent Orangists from retaining employment.

On 14 June 1796, he introduced another motion to discharge and immediately suspend 700 artillerymen garrisoned in Amsterdam, some of whom had been involved in riots.

[3] Initially, Aaninck was a follower of the radical priest Pieter Witbols, but over time he adopted a more moderate stance.

[3] Following the coup d'état of 22 January 1798, Aaninck was among the members who resigned in protest, as the regulations to which they had sworn an oath had been abolished.