He heads the Sami and Indigenous Rights Group, and has written extensively on indigenous peoples' rights under international law as well as on the indigenous Sami people's rights under domestic law. He has substantial experience practicing indigenous peoples' rights, predominantly within the UN system; Ahren was involved in the negotiations that led to the adoption of the UN Declaration on the Rights of Indigenous Peoples. He was also a member of the Expert Group that produced the draft Nordic Sami Convention, and has participated in the negotiations on various instruments being deliberated under the auspices of the World Intellectual Property Organization and the Convention on Biological Diversity.