5.  The applicant was born in 1968 and lives in Bremen. 6.  The applicant is a supporter of, inter alia, Werder Bremen football club, which plays in the German Federal Football League, and attends the club’s football matches regularly. 7.  Since 3 September 1996 the applicant has been registered by the Bremen police in a database on persons prepared to use violence in the context of sports events. Between 3 September 1996 and 24 May 2003 eight different incidents in the context of football games in which the applicant was considered to have been involved were listed. The applicant is further registered in a nation-wide database set up in 1994 on persons prepared to use violence in the context of sports events. In that database, persons are entered against whom criminal investigation proceedings were opened for offences in the context of sports events. 8.  On 10 April 2004 the applicant and some thirty to forty other football fans travelled from Bremen to Frankfurt am Main by train in order to attend the match of Eintracht Frankfurt football club against Werder Bremen football club. 9.  The Bremen police had previously informed the Frankfurt am Main police that some thirty to forty persons prepared to use violence in the context of sports events (so-called category C hooligans) planned to travel from Bremen to Frankfurt am Main. 10.  On their arrival at Frankfurt am Main central station, the Frankfurt am Main police verified the identity of the members of the Bremen group of football fans. The majority of its members were considered by the police to be football hooligans prepared to use violence. The applicant had further been identified by the Bremen police as a “gang leader” of the Bremen hooligans. The police searched the members of the group and seized a mouth protection device and several pairs of gloves filled with quartz sand found on members of the group other than the applicant. 11.  The group, placed under police surveillance, went to a pub. When the group left the pub, the police noted that the applicant was no longer with the group. He was then found by the police in a locked cubicle in the ladies’ bathroom of the pub. He was arrested by the police there at approximately 2.30 p.m. and brought to the police station close to the football stadium; his mobile phone was seized. 12.  The applicant was released at approximately 6.30 p.m. on the same day, one hour after the football match had ended. His mobile phone was returned to him on 15 April 2004. 13.  On 13 April 2004 the applicant lodged a complaint with the Frankfurt am Main Police Headquarters. He claimed that his detention on 10 April 2004 and the seizure of his mobile phone had been unlawful. 14.  On 17 August 2004 the president of the Frankfurt am Main police dismissed the applicant’s complaint. He found that the applicant’s complaint was inadmissible. The applicant’s detention constituted an administrative act which had become devoid of purpose by the lapse of time, as he had been released prior to lodging his complaint. Likewise, the seizure of his mobile phone had become devoid of purpose as the phone had been returned to him on 15 April 2004. 15.  The president of the Frankfurt am Main Police further considered that, in any event, the applicant’s complaint was also ill-founded. Relying on section 32 § 1 no. 2 of the Hessian Public Security and Order Act (see paragraph 33 below) the president found that the applicant’s detention had been necessary in order to prevent the imminent commission of “a criminal or regulatory offence of considerable importance to the general public”. Having regard to the information available to the police, it had to be expected that there would be an altercation between hooligans from Bremen and from Frankfurt am Main in or in the vicinity of Frankfurt, which would entail the commission of criminal or regulatory offences, in the context of the football match. As a rule, the time and place of such altercations were agreed on in advance by the groups of hooligans concerned. The applicant was considered to have attempted to evade police surveillance in order to arrange an altercation between hooligans. He was known to the Bremen police as a “gang leader” of the Bremen hooligans. He had further been observed speaking to a hooligan from Frankfurt am Main in the pub. He had further attempted to hide in the ladies’ bathroom of that pub. In order to prevent altercations between the groups of hooligans being arranged, it was indispensable to detain the applicant so as to separate him from the other members of the group. Furthermore, he could be released just one hour after the end of the football match, when the Frankfurt am Main and Bremen hooligans had left the stadium and its surroundings and were no longer in the applicant’s vicinity. 16.  Furthermore, the seizure of the applicant’s mobile phone, based on section 40 no. 4 of the Hessian Public Security and Order Act (see paragraph 36 below), had been lawful. Having regard to the hooligans’ usual practice, it had to be assumed that the applicant would use his mobile phone in order to contact other hooligans from Frankfurt am Main and Bremen in order to agree on the details of the hooligans’ altercation. It had therefore been indispensable to seize the telephone and not to return it immediately after the end of the football match in order to prevent such an altercation. 17.  On 6 September 2004 the applicant, who was from then onwards represented by counsel, brought an action against the Land of Hesse in the Frankfurt am Main Administrative Court. He requested the court to declare that his detention on 10 April 2004 and the seizure of his mobile phone had been unlawful. He argued that he was not a “gang leader” of a group of football hooligans, had not planned to arrange an altercation between hooligans or to commit an offence and had therefore not posed a threat which would justify his detention. He had not hidden in the ladies’ bathroom but had gone there because the men’s bathroom had been in a state excluding its use. 18.  On 14 June 2005 the Frankfurt am Main Administrative Court, having held a hearing, dismissed the applicant’s action. It found that the applicant’s detention on 10 April 2004 and the seizure of his mobile phone had been lawful and had not breached his rights. 19.  The court had heard the applicant and a witness, police officer G., who had been present during the police operation on 10 April 2004. The latter had confirmed that the group from Bremen the police considered to be hooligans prepared to use violence had already consumed a considerable number of alcoholic beverages during the train trip. He had added that during a search of the members of the group in Frankfurt am Main, a mouth protection device and several pairs of gloves filled with quartz sand had been found, which were instruments typically used by hooligans during altercations. During these clashes, offences such as bodily assault and breach of the peace (Landfriedensbruch – that is, acts of violence against persons or things committed jointly by a crowd of people in a manner which endangers public safety) were committed on a regular basis. He had personally told the group that they would be accompanied to the football stadium by the police and that every person leaving the group would be arrested. He had considered the applicant to be the leader of the group at that time. When entering the ladies’ bathroom, he had come across a man from Frankfurt who had claimed “to have nothing to do with the whole thing”. When he had then found the applicant in a locked cubicle of the ladies’ bathroom, the latter had not given any plausible explanation as to why he was there. When the applicant’s mobile phone had then rung, it had displayed a male name and the addition “Ftm.”. 20.  The Administrative Court found that the applicant’s detention for some four hours had been lawful under section 32 § 1 no. 2 of the Hessian Public Security and Order Act. It considered that in the circumstances of the case, it had been reasonable for the police to conclude that the applicant’s detention had been necessary to prevent the commission of considerable offences, such as bodily assault and breach of the peace. The applicant had attempted to evade police surveillance. As the applicant was a hooligan considered by the Bremen police to be a “gang leader” and was registered in a database of the Bremen police as a person prepared to use violence in the context of sports events, that conclusion had been appropriate. Moreover, it was a well-known practice of football hooligans, confirmed by witness G., to set up altercations. It was uncontested that the applicant had been in contact with a person considered by the police to be a hooligan from Frankfurt am Main. 21.  The Administrative Court further considered that the seizure of the applicant’s mobile phone had been lawful under section 40 no. 4 of the Hessian Public Security and Order Act. The applicant had had to be prevented from making arrangements for an altercation between hooligans both during his detention and directly after his release. It had not been possible to return the mobile phone to the applicant the next day as he did not live in Frankfurt am Main and had therefore been unable to pick it up on that day. 22.  On 1 February 2006 the Hessian Administrative Court of Appeal dismissed the applicant’s request to be granted leave to lodge an appeal against the Administrative Court’s judgment. 23.  The Administrative Court of Appeal found that there were no serious doubts as to the correctness of the Administrative Court’s judgment. It stressed that a person’s detention, having regard to the serious restriction of the right to liberty it entailed, was only indispensable within the meaning of section 32 § 1 no. 2 of the Hessian Public Security and Order Act if concordant facts in the circumstances of the case warranted the conclusion that it was very likely that a criminal or regulatory offence would be committed in the imminent future by the person detained and that, thereby, the general public’s interest in security would be seriously affected. The Administrative Court had convincingly found that, having regard to the circumstances and the information available, it had been reasonable for the police to assume that an altercation, entailing bodily assaults and breaches of the peace, between hooligans prepared to use violence had been imminent. It had further been reasonable for them to assume that the applicant’s detention had been necessary to prevent such an altercation. 24.  The Administrative Court of Appeal noted that at the time of the applicant’s arrest, the Frankfurt am Main police had had at their disposal information transferred to it by the Bremen police that the applicant was member of a group of football fans prepared to use violence (so-called category C hooligans) and was known as a “gang leader” of that group. The transfer of such information was justified under the provisions of the Länder on data transfer between police authorities. In any event, it was the Bremen police transferring the data in question, and not the Frankfurt am Main police receiving that information, which were responsible for the legality of the collection and transfer of the data in question. Therefore, the question whether the Bremen police had lawfully collected and stored data concerning the applicant was not to be determined in the present proceedings, which had been brought against the Land of Hesse, which was represented by the Frankfurt am Main Police Headquarters. Furthermore, the entries on the applicant in the database of the Bremen police had not been known to the Frankfurt am Main police on 10 April 2004 and the latter had not, therefore, based its assumptions concerning the applicant on those entries. 25.  The Administrative Court of Appeal further did not share the applicant’s view that, contrary to the Administrative Court’s findings, the police could not reasonably have concluded that the applicant’s detention was necessary to prevent the commission of an offence in the imminent future. The mere fact that the police had seized objects they had considered dangerous from the Bremen group of hooligans and that they had accompanied that group to the football stadium would not have sufficed to exclude an altercation between hooligan groups. Moreover, simply asking the applicant to rejoin the group of Bremen football supporters after he had been found by the police in the ladies’ bathroom would not have been sufficient to prevent the risk of an altercation between hooligans being arranged. Likewise, the police had not been obliged to conclude that separating the applicant from the Bremen group of hooligans would be sufficient to prevent such an altercation. As had been confirmed by the applicant himself, such clashes did not, as a rule, take place in or close to the football stadium, but in different places. 26.  The Administrative Court of Appeal further endorsed the Administrative Court’s finding that it had been reasonable for the police to assume that the applicant, having been identified as a group leader prepared to use violence, would be personally involved in the altercation with the Frankfurt hooligans. 27.  Finally, the Administrative Court of Appeal also confirmed that the police had been authorised to seize the applicant’s mobile phone under section 40 no. 4 of the Hessian Public Security and Order Act. The applicant’s telephone had been seized in order to prevent him from using it in order to commit an offence. 28.  On 1 March 2006 the applicant lodged a constitutional complaint with the Federal Constitutional Court. He complained that his detention had breached his right to liberty. There had not been any reason to assume that he was about to commit a criminal offence. Furthermore, the administrative courts had wrongly refused to examine whether his registration in the database of the Bremen police as a “gang leader” of persons prepared to use violence in the context of sports events was lawful. This registration led to him being prohibited by football clubs to enter football stadiums and to travel restrictions being imposed on him by the police during international football matches. Therefore, the fact that he had never been able to lodge an appeal against this registration had violated his right to liberty. Moreover, in the applicant’s submission, the seizure of his mobile phone had violated the right to secrecy of telecommunications and his property rights under the Basic Law. 29.  On 26 February 2008 the Federal Constitutional Court, without giving reasons, declined to consider the applicant’s constitutional complaint (file no. 2 BvR 517/06).