21.—(1) It shall not be lawful for any person to be a member of an unlawful organisation.

(2) Every person who is a member of an unlawful organisation in contravention of this section shall be guilty of an offence under this section and shall—

(a) on summary conviction thereof, be liable to a fine not exceeding F8[€3,000] or, at the discretion of the court, to imprisonment for a term not exceeding F8[12 months] or to both such fine and such imprisonment, or

(b) on conviction thereof on indictment, be liable to F8[a fine or imprisonment for a term not exceeding 8 years or both].

(3) It shall be a good defence for a person charged with the offence under this section of being a member of an unlawful organisation, to show—

(a) that he did not know that such organisation was an unlawful organisation, or

(b) that, as soon as reasonably possible after he became aware of the real nature of such organisation or after the making of a suppression order in relation to such organisation, he ceased to be a member thereof and dissociated himself therefrom.

(4) Where an application has been made to the High Court for a declaration of legality in respect of an organisation no person who is, before the final determination of such application, charged with an offence under this section in relation to that organisation shall be brought to trial on such charge before such final determination, but a postponement of the said trial in pursuance of this sub-section shall not prevent the detention of such person in custody during the period of such postponement.