After his expulsion,[2] in 1969 he was suspected of having sabotaged a Boston Chemical plant, which produced defoliant used in the Vietnam War, but he was immediately released.
In the late 1969, with Oreste Scalzone and Toni Negri, he was one of the founders of the far-left organisation Potere Operaio,[2][3] and later he was a member of Autonomia Operaia.
[3] In particular, he was accused of having acted as a negotiator (through one of the kidnappers, Valerio Morucci) between the Italian Socialist Party and the terrorists who were allegedly detaining Moro.
[5] Documents left by the journalist Mino Pecorelli after his murder also hinted at an involvement of Piperno in the kidnapping.
[3] Piperno returned to Italy from Canada in 1990,[7] and became active locally in his hometown, Cosenza, creating the cultural association Ciroma.