Ten policemen and three former colleagues launched a legal challenge yesterday to the force's ban on officers forming trade unions. The applicants filed a submission for a judicial review in the High Court arguing the decision of Police Commissioner Tsang Yam-pui to uphold the ban was unconstitutional and unlawful. They say the ban violates the Basic Law and in particular Article 27, which guarantees the right and freedom to form and join trade unions and strike. One of the applicants, former inspector Bernard Lau Kwok-fai, argues that the mainland and countries such as Germany and the United States permit the formation of police unions. Lau was dismissed in June following an indecent assault conviction. He sought a judicial review of the ban in August but was denied because he was no longer a police officer. The other applicants are two former and 10 serving constables. The force's case is that police officers are banned from trade union activities under the terms of the Police Force Ordinance and that the law conforms to the Basic Law. The applicants argue that cannot be so, because the legislation was enacted before the Basic Law came into effect in 1997. 'With the promulgation of the Basic Law ... the prohibition against officers becoming members of trade unions should cease to have force,' the submission says.