ing to law, unless it is proved that the non-disclosure of the unknown fact in time is wholly or partly attributable to that person. 7. No migrant worker or member of his or her family shall be liable to be tried or punished again for an offence for which he or she has already been finally convicted or acquitted in accordance with the law and penal procedure of the State concerned. Article 19 1. No migrant worker or member of his or her family shall be held guilty of any criminal offence on account of any act or omission that did not constitute a criminal offence under national or international law at the time when the criminal offence was committed, nor shall a heavier penalty be imposed than the one that was applicable at the time when it was committed. If, subsequent to the commission of the offence, provision is made by law for the imposition of a lighter penalty, he or she shall benefit thereby. 2. Humanitarian considerations related to the status of a migrant worker, in particular with respect to his or her right of residence or work, should be taken into account in imposing a sentence for a criminal offence committed by a migrant worker or a member of his or her family. Article 20 1. No migrant worker or member of his or her family shall be imprisoned merely on the ground of failure to fulfil a contractual obligation. 2. No migrant worker or member of his or her family shall be deprived of his or her authorization of residence or work permit or expelled merely on the ground of failure to fulfil an obligation arising out of a work contract unless fulfilment of that obligation constitutes a condition for such authorization or permit. Article 21 It shall be unlawful for anyone, other than a public official duly authorized by law, to confiscate, destroy or attempt to destroy identity documents, documents authorizing entry to or stay, residence or establishment in the national territory or work permits. No authorized confis116