Recognizing Hopf algebroids defined by a group action

Let A be a complete noetherian regular local ring, and suppose that S is a profinite group acting continuously on A via ring homomorphisms. Let Γ=Mapc(S,A), the algebra of continuous functions from S to A. Then (A,Γ) has a canonical structure of a complete Hopf algebroid, determined by the action of S on A. We give necessary and sufficient conditions for a general complete Hopf algebroid to be of this form. Applications to Morava theory are also discussed.