"The privacy of correspondence, posts and telecommunications shall be inviolable. -- Restrictions may be ordered only pursuant to a law."
This article introduces confidential communication as a fundamental right. No one is allowed to read our letters, emails or messages or eavesdrop on our phone calls. Not even parents, partners, teachers or the police can open our packages, nor, for instance, the Postmen can reveal from where a letter or packet comes.
But there is one exception: when someone is planning a crime, the police can read that individual's letters and messages and and listen in on their conversations. Even then, the police need permission from a court to do so. The court allows such measures only if the police have sufficient reasons for suspicion.
The BAMF has been assessing asylum seekers' cell phone data since 2017. It is legally controversial whether this is justified or a violation of the privacy of correspondence. So far, there is no resolution.