What actors and actresses appeared in Guardians of the Wild - 1928?

There seems to be a misunderstanding. There is no movie called "Guardians of the Wild" from 1928. There is a 1928 film called "The Last Warning", a silent film directed by Paul L. Stein. It stars Laura La Plante and John Bowers.

It's possible you're thinking of a different film or that there's a more recent film with a similar title. Can you clarify what film you're asking about?