IMHO that's all that needs to be said. This is exactly how it should be. This is a problem for which laws were written and this is something the judges should eventually have the power to decide upon.
If we don't like their decision, it's up to us to change the laws.
Civil disobedience is also not correct. Civil disobedience is the refusal to obey laws, not the refusal to uphold them. People participating in civil disobedience do it with the understanding that they can (and should) be prosecuted for such. They do so to act as martyrs.
The law can be very wrong sometimes, and it's the responsibility of an ethical human being to disobey such laws, whether by non-application or nullification, until such time as those laws are corrected.
My response would be that, in such cases, there exist two sets of conflicting laws. The national law, which was not being broken, and the supra-national law regarding human rights and war crimes, which was. So that is actually an example of rule of law being upheld, just not national law.
The bottom line is, you need to be really, really careful when you start arguing for "ethics" and "morality" as a basis for execution of law. For instance, to make a concrete example: It could be argued that based on the ethics and morality of the Nazis, that the mass murders committed under the Holocaust were in fact them morally disobeying those supra-national human rights laws. Who are you to say that the Nazi morality is wrong? You can't point to the agreed-upon supra-national human rights laws, because you are in fact arguing that law should be violated based on morality!
In fact, one of the ways to view law is as an encoding of the morality of the society it covers. Sometimes laws, being fixed entities, and society, being ever changing, drift apart over time. Same as software drifts from the requirements of business if not kept up to date. It usually takes an example like this German one to point out the absurdity, and if the law really is no longer part of the society's morality, becomes fairly easy for lawmakers to fix. (As a reminder, this law being invoked is very old -- from when Germany was a monarchy and insulting dictator kings was morally a very serious crime!)
This is a problem.
You're promoting anarchy which isn't a workable system AFAICT - the gaoler believes it's wrong not to accept a bribe because that will mean his child goes hungry, so he should release the criminal despite the democratically elected officials having openly created a law that has not been opposed by the people (eg in massed protest)?
The alternative is a rejection of conservatism in the worst way: the state can change too quickly for society to have a proper discourse on whether we made a mistake or not. "Revolution" is a relatively positive word these days and it's easy to forget that actual lives are often lost when mob mentality takes precedent over rule of law.
That said, my take is that if the law is unjust, I prefer the law to be overturned rather than not prosecute on the law or rely on disobedience.
In this case prosecuting may create enough bad will that people will find it unpalatable and work to have it overturned to the dismay of foreign "dignitaries".