The optional grounds for refusal are basically the following: a) the fact that the form is incomplete, b) an eventual breach the principle of ne bis in idem, c) the facts under investigation in the foreign state are not punished as criminal offence in Portugal, d) the criminal proceedings are statute-barred under the internal law, and Portugal has jurisdiction over the facts, e) there is an immunity of the defendant that under Portuguese law would prevent the execution of the supervision measure, the person subject to the supervision measure would not be be charged in Portugal by reason of age.