I was execting to disagree with the points made by the "remian" essay, but there... aren't any? It's just a recounting of how the marbles got where they are.
To me, the discussion about the means of acquisition is only relevant if the debate is "Should the UK be legally compelled to return the marbles", but if the debate is "Should the UK return the marbles" then I don't feel its relevant either way.
There is no tenable contemporary argument for keeping them in the Bristish museum, IMO.
It seems to be all variations of "You gave me for safekeeping, now it's mine".
The weird thing for me is that there is no strong cultural link between Britain and the marbles. These might as well be the Rapa Nui Moai statues. Even the British Museum having the Liberty Bell would make more sense from an historic POV.
Again, just my opinion, but it seems like the British museum is using this to fight back against a very British malaise: not handling well with the slow decline of its status as a world power.
I live not too far from the British museum, and as I see it I have two options.
1. Convenient access to some of the marbles, or I could fly to see an incomplete Parthenon.
2. No convenient access to the marbles, but I could fly to Greece to see a more-complete Parthenon.
The primary argument relates to the authority to remove the marbles granted by the 'lawful' government at the time. The government at the time was a subsidary of the Ottoman empire, Greece having been conquered roughly 400 years previously. The government was composed mainly of Turks though with numbers of Greek collaborators. The Turks didn't particularly about the Greek culture at the time and especially not about the ancient Greek culture.
Now imagine a similar event occurring during WWII: a party from a third country obtaining authority by the 'lawful' (at the time) Vichy government (a Nazi subsidiary) to remove invaluable French art from the Louvre. What position would you hold today? These are essentially the same. Can a government that obtains its legitimacy through the imposition of force by a conquering power be considered 'lawful', and it's decisions hold legal force in any subsequent dislodgement of that conquering power?
That's what this all boils down to. For me, the Ottomans were as 'lawful' a government of Greece as the Vichy were in France i.e. not lawful.
They were looted. Full stop. The British Empire acquired them through conquest, much like most of the contents of the British Museum.
I think I'd have less of a problem with it if they just kind of owned it. Rather than pretend there's some sort of noble intent with keeping the spoils of conquest.