The fantasy drama, from Life On Mars creators Matthew Graham and Ashley Pharoah, followed two angels who work as barristers to help troubled humans.
West played Zak Gist on the show and broke the news of its cancellation on Twitter.
"Alas there will be no more Eternal Law," he confirmed. "Not enough people watched it. A thousand thanks to those of you who did, and said such kind things."
He added: "I'll miss Zak and the gang enormously, but I'm very proud of the work we did. And we'll always have York. Onward!"
Also starring Orla Brady, Ukweli Roach and Tobias Menzies, Eternal Law drew 5.43m viewers when it premiered on ITV1 in January.
However, by the sixth and final episode, audience numbers had dropped to just 2.95m.
Watch Digital Spy's interview with Eternal Law star Orla Brady below: