There are no mandatory grounds for refusal of the recognition/execution of a supervision measure.
The optional grounds of refusal are basically the following: a) the fact that the certificate is incomplete, b)an eventual breach of the principle of ne bis in idem, c) the facts under investigation in the foreign state are not punished as criminal offence in Portugal (with the exception of the offences mentioned in article 14 of the FD that won´t be verified on double criminality), d) the criminal proceedings are statute-barred under the internal law, if Portugal has jurisdiction over the facts, e) the existence of an immunity of the defendant that under Portuguese law would prevent the execution of the supervision measure, f) the person subject to the supervision measure would not be be charged in Portugal by reason of age;