"[P]rovision may be made for depriving individuals of their right to vote and to be elected, but only subject to the following cumulative conditions. ii. it must be provided for by law; iii. the proportionality principle must be observed; conditions for depriving individuals of the right to stand for election may be less strict than for disenfranchising them; iv. The deprivation must be based on ... a criminal conviction for a serious offence. v. Furthermore, the withdrawal of political rights ... may only be imposed by express decision of a court of law. "