Which German constitutional decision is cited as a strong example of a state's deontological commitments?

Question

Accepted Answer

The Federal Constitutional Court's ruling striking down the power to shoot down a hijacked passenger aircraft — the state may not kill innocent people to save a greater number.
After the 2001 attacks, Germany's Aviation Security Act (Luftsicherheitsgesetz) gave the armed forces the power to shoot down a passenger aircraft that was being used as a weapon against people on the ground. In 2006 the Federal Constitutional Court (Bundesverfassungsgericht) held the provision unconstitutional.
The reasoning is deontology in its purest institutional form. The passengers and crew are innocent, and the state would be killing them deliberately in order to save others. Doing so treats them as objects — as a means to rescuing the people on the ground — and that is incompatible with human dignity and the right to life. The number of people who would be saved does not enter the calculation, because the point of the guarantee is that it is not the kind of thing that can be traded against a quantity.
The case is the clearest available demonstration that a legal order can be constitutionally deontological: the constraint binds even when the arithmetic is overwhelming and even when everyone on the aircraft will die anyway.
It also illustrates the moral difficulty rather than dissolving it — the scenario was later dramatised in Ferdinand von Schirach's courtroom play Terror, in which the audience votes on the pilot's guilt, and the vote goes for acquittal far more often than the court's reasoning would suggest.
Go deeper:

Bundesverfassungsgericht: Authorisation to shoot down aircraft is void — the court's own English press release on the 2006 judgment — the reasoning in its own words.
 Wikipedia: Luftsicherheitsgesetz — the act, the judgment and the political attempts to revive the power since (German).
 Wikipedia: Terror – Ihr Urteil — von Schirach's courtroom play on the same case, where the audience votes — and usually acquits (German).