May a union advertise its services in a company?
 One of the components of the freedom of association guaranteed in Article 9(3) of the Basic Law (Grundgesetz) is the constitutionally protected right of unions to pursue union activities. The unions' right to also advertise for new members within individual companies derives from, among other things, this freedom to pursue union activities.
However, there are no legal rules on which specific advertising measures are permissible. According to the principles developed by the courts, the permissibility of advertising measures will always depend on the circumstances of the individual case. The courts make the permissibility of company-internal advertising subject to a general proviso that it may not interfere with the employer's interest in having smooth workflows or harmony in the workplace. Nor may it conflict with the employer's interest in confidentiality and security. It is true that union advertising may not be reduced to an essential minimum. Nonetheless, it must always consider the justified interests of the employer. In addition, the rights of the employees who the union seeks to recruit must also be respected. For this reason, union members are, of course, not permitted to "pressure" their colleagues into joining the union.
Judgment of the Federal Labor Court
In light of the fact that the courts have elaborated very few clear principles, the limits of what can be considered permissible advertising and what cannot depends on the facts of a small number of individual cases. The Federal Labor Court recently decided another case on this topic (Judgment of 20 January 2009, Case Ref.: 1 AZR 515/08) in which it held that the union that is responsible for collective bargaining in a company may also send advertising and other information to the company e-mail addresses of employees. According to the Federal Labor Court, this will still apply where the employer has expressly prohibited its employees from using e-mail for private purposes. The employer can first demand that the union cease what it is doing when sending e-mails results in noticeable interference with workflows or economic burdens which are attributable to the union.
On the other hand, the Federal Labor Court held in a decision on 23 September 1986 that the right to pursue union activities does not go so far as to permit a union to use a company-internal postal system to send union advertising material to employees. The Federal Labor Court did indeed also stress at that time that unions are entitled in principle to advertise within a company. However, in the Court's view such right did not extend so far as to allow a union to use property belonging to the employer or its staff. Since the union had, however, used the labor of the employees working in the mail room, the advertising was impermissible.
Technical progress has benefited the unions: since sending and receiving e-mail in normal quantities generally does not result in any particular expense or interfere with workflows, the opportunities for advertising have grown. According to the decision of the Federal Labor Court, a union may use the work e-mail addresses of employees so that it can get in touch with them easily and try to recruit them to join the union.
Nonetheless, advertising measures by unions are not restricted to mail or advertising e-mails. Instead unions are entitled in principle to exercise their right to enter the workplace in order to advertise for members "on location". In this connection, it is irrelevant whether the union already has some members among the workforce. According to a landmark case handed down by the Federal Labor Court on 28 February 2006, a union may in addition advertise its services by sending a non-company union member into a company to advertise for it, for example, by distributing its union newspaper or other information material. However, it has to ensure at all times that advertising does not interfere with or disturb workflows. Therefore, an employer can prohibit a union from having company employees distribute advertising material during business hours.
Attaching advertising stickers to helmets supplied by the employer would also be to exceed the boundaries of what is permitted since this would involve the property of the employer. On the other hand, the union may put up posters on a company pin board used for internal communication. Nonetheless, if the material posted contains comments on general political issues which are not directly related to safeguarding working and economic conditions, such content will go beyond the limits of permissible union advertising. Unions are therefore not authorized to advertise in the workplace for the party of their choice prior to a general political election. On the other hand, they are permitted in the case of works council elections to intervene and specifically support "their" candidate.