A judicial challenge in the UK to a government decision to invest more than $1bn in Mozambique’s Cabo Delgado natural gas project has resulted in an unusual stalemate: one of the two judges upheld the investment decision, but the other found the approval was based on inadequate information about the climate change risks, and was therefore unreasonable.

According to UK legal experts, it’s the first time high court judges have given a split ruling in a constitutional matter...