Okay, problem with this claims logic:
1. Shadovar was founded by Pian en Luries, yes, and D'Hara secede from Shadovar. But the issue here is that backing a colony does not in any sense confer claim. Madina never had claim to Golden Farrow. Aurvandil has no claim to Falkirk. That's the whole point of a COLONY, it's a SEPARATE legal entity.
2. Furthermore, supra-national entities like the Lurian Empire did not exist until recently: as such, they cannot have received claims that originated on a trans-national basis prior to their existence. You cannot create an entity then assert that you magically got claims from decades earlier. Well, you can: but it's smoke and mirrors completely without substance.
3. Even if you did have claim under Shadovar, no heir of Shadovar-contra-D'Hara exists. Find me a descendant of Shadovar's rulers who can press the claim, a direct descendant with some kind of real claim. Simply because you were bros with a realm doesn't mean you are the lagl inheritor of their rights and liabilities.
4. Luria Nova has engaged in treaties with D'Hara while D'hara held Qubel Lighthouse and/or Port Raviel as its capital city. Ask the Palestinian Authority what happens to your legal standing when you sign agreements with another country while they hold your land: they gain legal sovereigntyu (hence why formal, non-shuttle agreements between the PLA and Israel are rare: Israel doesn't want to grant them de facto statehood, and PLA doesn't want to grant de jure control of Jerusalem). Lurian realms have in fact engaged in numerous instances of direct diplomacy and agreement and treaty with D'Hara, and, under terms of estoppel, cannot cease this service once rendered. Once you sign away Qubel and Raviel by signing establishing treaties with the owners of Qubel and Raviel, you recognize the transfer. Admittedly the case is not as solid as if you had directly signed them away, and Luria's frequent protestations against D'Hara serve as notice of dispute in legal terms, but there's another issue....
5. Effective sovereignty can create de jure sovereignty under international law. See the Pedra Brance case for details (specifically relating to island claims, as it happens). This idea is in fact an extension of an earlier medieval concept that if you perform the actions of a soveriegn and nobody else performs the actions of a sovereign for a long time, then you are in fact a sovereign.
6. Legally, it is not clear that Luria Nova has inherited Pian en Luries' claims. The persons, yes, but Lurian monarchy, you have asserted, is an institutional, not personal, title. As such, Alanna has no claim to Shadovar due to being monarch: that was a de jure claim of the Pianian monarchy, not Alanna. Unless she retains the title Queen of Pian en Luries, she can't make that claim. If the Pianian monarchy is institutional, the demise of Pian en Luries would suggest that monarchy is gone, and has been replaced by Novan monarchy. You may assert that you are continuing Pianian monarchy, but the circumstances of succession to Pian en Luries do not lend credibility to this (unlike Solaria, where the Novan monarchy is the right pressor of claims given their representation of Malus Solari, who holds those claims personally rather than institutionally).
For these reasons, Luria Nova has no "claim" in any legal sense, or, at the very most, an extraordinarily weak claim.
So why does D'Hara have claim?
1. Effective sovereignty as noted above. D'hara has controlled the islands for way long enough.
2. Recognition by all sovereign states. No state in Dwilight has failed to recognize D'Hara as sovereign of the isles. Even Luria Nova has done that.
3. Secession by Katayanna Ogren was not protested by Luria Nova at the time, I believe, and certainly did not get material opposition. Lack of complaint is consent in international law, ESPECIALLY regarding land claims (see Senkoku/Diaoyu island dispute for another example of how this plays out).
4. Even if Pian en Luries had some macro-claim to the islands from colonization, Lurian practice is such that secession is legitimately claim-conferring providing the seceder is ballsy and Very Lurian. Katayanna Ogren was indisputably Lurian and very ballsy. This secession, by virtue of being basically the normal practice of politics within Lurian cultures, cannot be regarded as splitting a claim. Rather, it was an "in-region" dispute between Lurian contender. The winner was a Lurian, Katayanna Ogren. She established a monarchy which has managed a clear succession to the present day. Under Lurian law, under the Lurian empire, even if Luria DOES HAVE CLAIM, there IS a legitimate "Lurian monarch" of the Tomb Islands. His name is Machiavel Chénier. At no point has Luria Nova ever made any argument that the established office of the Dragon King is illegitimate, and Luria Nova has never renounced Katayanna Ogren's Lurian-ness. By now, again under estoppel and the presence of ongoing formal dispute, such renunciation would be worthless.
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Additional things Luria Nova could do (or could have done) to legally undermine D'hara's claim, aside from their currently extant practices of protest and denial of formal recognition:
1. Denounce the office of the Dragon King
2. Appoint a different person Dragon King
3. Appoint shadow-dukes and shadow-lords
4. Send priests, courtiers, and traders to carry out surveys, censuses, and administrative tasks
5. Refuse to ever negotiate directly with D'Hara
6. Welcome D'Hara into the Lurian Empire, then demand rights of revocation
7. Include in negotiations that Luria Nova will only sign peace treaties in the Capital of D'Hara, defined as Paisly, no matter D'Hara's claims to the contrary
INTERNATIONAL LAWYER'D.
PS- If it seems like I've spent to much time thinking about this, it's because my graduation thesis was about island claim law and the status of several ongoing land claim disputes.
