'Constitution' arguments are used by ones in power only to server their agenda. Constitution argument won't save us from the surveillance. Most of the time western countries play 'national security' and 'think of the children' to circumvent the constitution and have ~100% success rate.
I don't feel like that's true in Germany. The constitutional court would like a word I guess. They have a pretty big history regarding surveilance and such.
So shouldn't be a concern then for Germans? Somehow I don't buy that. See for example https://forum.torproject.org/t/tor-relays-artikel-5-e-v-anot... and that's not an isolated event. Before that were jabber chat nodes.
So did they go to court? I think that would be crucial to rectify that. If not, they let the rogue agents have a free hand.
Be involved in the legal battle (especially with the government) is a punishment already. The state has unlimited power to haras and do that frequently.