Those are the simple words of article 102 of the Basic Law.
Nowadays most developed countries have abolished capital punishment and many have done so constitutionally. But in 1949 constitutional abolition was still unusual. We Germans tend to over-idealize this decision, thinking it a reaction to Nazi atrocities. In fact it was at least partially meant to save the neck of war criminals. Still, it is a civilizational achievement to be proud of.
Capital punishment may be necessary in third world countries where long term imprisonment is not an option. And at earlier points of our history it might have been necessary for the same reason. But in a modern industrialized nation there is no excuse for still imposing it.
The one downside I see in this achievement is how it moves the Overton window. With death totally off the table the debate moved on tho lifetime imprisonment. After pardons became standard the Federal Constitutional Court ordered a formalized review scheme. Nowadays the average length of a "life sentence" is just under 20 years.
I understand the humanitarian instinct behind that development. We must avoid turning criminal punishment into vengeance. But I still think it is misguided. The deterrent effect of real lifetime imprisonment is pretty much an empirical fact, though it probably wasn't as certain at the time of the constitutional judgment. Also, I don't think we know how to resocialize everybody. In the case of sexual murders we now talk of resocialization if the risk of recidivism is reduced as far as it is reducible. But that is still a far cry from reducing it to the risk of normal people committing that kind of crime. Not locking some people up for their lifetime has too high a cost in innocent life and I don't think the rights of murderers can justify that. The laudable effort not to treat criminals as objects ends up treating innocents as objects expendable in the course of our humanitarian efforts. I don't think that leaves us with much of a standing to criticize Americans still executing people. Also, I fear an eventual backslash bringing capital punishment back.
But still having done away with capital punishment is among the greatest achievements of the Basic Law.