I am no expert on German testamentary law, but I did find it surprising. From reading news about the German nobility I had the strong impression that immoral and discriminatory house laws which are stipulated in testaments continue to be upheld, with the best-known example being the disinheritance of daughters to pass estates to sons.
I was also surprised that the judge expressed a conclusion on the validity of the testamentary requirements because there was no practical need to reach any conclusion on that question, given the court's ruling that Gustav fulfilled all of the requirements, regardless.
It's not so much a question of testamentary law. It might not be so evident from the outside, because it's a cultural and historical thing. Being Austrian, I know that Austria and Germany have extremely strict laws aimed at preventing any kind of resurrection of National Socialism. Reading the Nazi terminology of "artfremdes Blut" (bringing another race's blood into the family
) I knew it would be extremely unlikely to find any court that would not declare it invalid.
Let's put it this way: while you may or may not get away with discrimination of any other kind (such as on the basis of sex with daughters being excluded from inheriting or even class with house laws/ wills stating that the heir must marry an aristocrat), you will
never get away with discrimination based on Nazi ideology.
The quote you posted states that the court doesn't have to decide on whether the demand that he not be married to a non-aristocratic woman is valid, because
a) He was not married to anyone.
b) The demand that he not be married to a non-aryan woman is unacceptable.
Basically, he could have been married to her and the court would have declared the will's demands invalid, based on the unacceptable demand for a certain type of blood alone.
Why the judge ruled on this, when there was no need to because Gustav was not married? Because the judge wanted to make it very clear that there is no legal validity to demands based on Nazi ideology. What I said above might explain why it's considered so important. No matter what else the will stated or the law states, declaring any kind of Nazi ideology illegal is considered of the
utmost importance by German law.
I have no command of legal German and relied on machine translation in order to read the ruling, therefore corrections are welcome. But in section 81 the judge (judges?) sets out their conclusion that the testamentary obligation on the heir's wife to fulfill the requirements for membership in the nobility association is invalid because it breaches the "good morals" clause in section 138 of the Civil Code.
It is not clear to me if the judge intends for that conclusion to apply to all of the Adelsgenossenschaft membership requirements (as ricarda suggests) or only the "non-aryan" part (as Princess_Eleanor suggests). Although section 81 of the ruling makes reference to the justification of protecting the family from outside blood, there is no explicit reference there to the "non-aryan" requirement.
Reading it again, I didn't quite read it correctly the first time. Apparently the part about being a member of the aristocracy does not need to be evaluated, because the demand that there not be any "artfremdes" blood (meaning literally no blood from another race, meaning a non-aryan race) makes the whole demand illegal.
So there is still no ruling on whether a will that demanded marriage to an aristocrat (without the demand for no blood from another race) would also be declared invalid. Therefore, I don't think this can be used as a precedent for cases where "only" the aristocratic demand, but no demands about blood (=race) are made.
So, I am quite sure that's not the one. 
