Commissioner of oaths for stat. declaration of common-law

[Bifidus]

Dear all,

My partner and I are applying for a work permit visa (I have been offered a Postdoc Fellowship, she is applying for a Open Work Permit) and we want to attach the IMM5409 Statutory declaration of common-law union. Problem is that, as it seems, a Commissioner of Oaths should sign the form, but we are living in Spain. Does anybody know if the "Commissioner of Oaths" should be Canadian or it could be Spanish? Could it be just a notary from Spain?

Thank you