Acheson was interested in Māori
land tenure and wrote a lengthy essay on the subject in 1913 arguing that Māori had clear customs and practices regarding land amounting to customary law. This essay was in opposition to the prevailing legal opinions at the time. He started work as a clerk at the
Native Land Purchase Board in 1914, and became a native land purchase officer in 1918, working in the
Hawke's Bay and
Wanganui areas. The following year, he became commissioner and a
land court judge in the
Taranaki-Wanganui area. In 1924 he moved to be land court judge in
North Auckland, where he remained until 1943. Major cases Acheson was involved with included whether the land court could recognise Māori claims to the
foreshore, and whether the
Treaty of Waitangi had legal weight.
Lake Tangonge,
Lake Ōmāpere and
Ōrākei were land disputes he played a significant role in. In 1925 Acheson proposed the Tokerau District Maori Land Board, of which he was president, fund a dairying scheme at
Te Kao. He believed this scheme would assist Northland Māori to develop their remaining lands and ameliorate the poverty of the area. Although the 1934 commission of inquiry into the Native Affairs Department administration supported his work, the
1935 Labour Government increased official supervision of the scheme. Acheson considered this government bureaucracy and his relationship with the Native Department and the Government became strained. In 1943, Acheson was forced to retire as land court judge. Financial problems of the Tokerau Board over the dairying scheme were the given reason, but his pro-Māori stance and poor relationship with the Government undoubtedly contributed. ==Political career==