Art. 117 PILA from 2022

Art. 117 b. Absence of a choice of law
1 In the absence of a choice of law, contracts are governed by the law of the state with which they have the closest connection.
2 Such a connection is presumed to exist with the state of habitual residence of the party that has to perform the characteristic obligation or, if that party has concluded the contract in the exercise of a professional or business activity, with the state where such party has its establishment.
3
Es besteht kein Anspruch auf Aktualität und Vollständigkeit/Richtigkeit.