According to the new military service law in Germany, men aged between 17 and 45 will need to request approval for stays abroad longer than three months.
The German Ministry of Defense confirmed the information to dpa on Saturday following press reports.
Chancellor Friedrich Merz's administration adopted a law at the end of last year to reintroduce military service - initially on a voluntary basis - in an effort to increase troop numbers.
The law, which came into effect on January 1, is a response to the threat posed by Russia, with Germany lagging behind in meeting NATO recruitment targets.
The program is aimed at increasing the number of soldiers in the Bundeswehr - the German army - from 180,000 to 260,000, with an additional reserve force expected to reach 200,000.
All teenagers will receive a questionnaire after turning 18 as the first step to assess their suitability and motivation to serve in the military. Men are required to fill out the form, while for women, completing the form is voluntary.
The newspaper Frankfurter Rundschau reported that men need Bundeswehr approval for long trips abroad.
A Ministry of Defense spokesperson confirmed the existence of this rule but stated that "approval is considered self-evident as long as the service is voluntary."
The military must know who spends long periods abroad, the spokesperson insisted, but refused to specify how many approvals have been requested since the beginning of the year.
He also mentioned that the rule has been in place since the Cold War era but has never been strictly enforced.