By Soon Minh
In March 2021, Boris Johnson outright rejected the possibility of returning the Parthenon marbles to Greece.  He claimed that they were “legally acquired” by Lord Elgin in the nineteenth-century and are now owned by the British Museum.
The Parthenon marbles are a collection of Greek sculptures, originally part of the temple of the Parthenon in Greece, but now supposedly property of the British Museum. They have grown to become a source of great controversy as Greece requests that “unlawfully removed cultural objects” be returned as part of the Brexit trade deal negotiations in 2020, which the UK ignored. 
Legal basis for British Museum’s ownership
The Museum is governed by a Board of Trustees, who have a fiduciary duty towards the British public.  Under this, the Board cannot dispose of museum artifacts except in very limited circumstances, none of which include repatriation. While Greece has argued that Elgin’s removal of the Parthenon marbles was illegal at that time, the British Museum’s ownership is currently protected by the British Museum Act of 1963 and the common law duty of fiduciary.
No international law compels the UK to return the Parthenon marbles.
Despite mounting pressure on the Museum to return the marbles, there seems to be little legal basis for Greece to reclaim them, unless it resorts to political manoeuvring through Brussels or otherwise. Boris Johnson’s recent statement that the Parthenon marbles “have been legally owned by the British Museum’s trustees since their acquisition” only further cements this.  It seems that so long as the British Museum Act of 1963 remains in force, the Parthenon marbles will remain on display in the British Museum.
 Hannah R. Godwin, Legal Complications of Repatriation at the British Museum, 30 Wash. Int’l L.J. 144 (2020).
 Ibid