In parliament, Sempastous served as member of the Committee on Economic Affairs. In addition to his committee assignments, he was part of the parliamentary friendship groups with Pakistan and Spain as well as of the French delegation to the Inter-Parliamentary Union (IPU).[2]
At the initiative of Sempastous and Benoît Simian, some twenty LREM deputies who had been elected in rural areas established their interest group within the party's parliamentary group in September 2018.[3]