James has a broad client base around New Zealand. He specialises in public law, with broad experience in the Treaty of Waitangi, Crown-Māori relationship, national security and governance.

A lawyer since 2012, he was a senior adviser to former Attorney-General Christopher Finlayson and Prime Ministers Sir John Key and Sir Bill English, and has practised on his own account since 2019.

In 2021 he co-authored with Christopher Finlayson He Kupu Taurangi, a history of Treaty Settlements under the National Government. He is currently writing the biography of former National Party Minister of Justice, Ralph Hanan.

James has a long-standing interest in New Zealand foreign policy and the arts, and served as a trustee of the New Zealand String Quartet from 2017 to 2023.