First, does the Kingdom of the Netherlands actually HAVE a Separation of Powers doctrine in its constitutional documents?
Second, are these "promises" or are they signed and ratified treaty obligations? I don't know about there, but in the US Constitution a treaty, once ratified by the Senate, has the same legal force as the Constitution itself. If this is true there, someone with proper standing could probably bring a suit demanding that the KoN fulfill its treaty obligations.
Thirdly, how did any court grant standing to a non-signatory organization? Can its decision that a bunch of busybodies have standing be appealed to a higher court?
Fourthly, does the KoN have the doctrine of Sovereign Immunity? If so, it cannot be sued without its prior consent. If it doesn't have that, now, can it create that right as existing in the past, as the UK can and has done, by an Ex Post Facto law? Actually, the UK removed a right (to compensation for war damages in enemy-controlled territory) in the case that I know of, but the principle that Ex Post Facto laws are legal can be extended ad infinitum.
Fifthly, I must quote that SoB, Andrew Jackson, after the Cherokee Tribe won (in the US Supreme Court) the right to stay in the East despite the Indian Removal Act, "They have made their ruling. Now let them enforce it." The point being that the judge's marshalls, baliffs, constables, whatever they are called, are not equipped to force the government to do what its military or the rest of its police forces "decline to acquiess" (to quote Capt. Barbossa from the first Pirates Of The Carribbean movie).