What structure is the poem Robin Hood and the Scotchman

Every ballad is a short story in verse, which dwells upon only on one particular episode of the story. There is certainly only one episode of the story in a ballad and the poet needs to complete the story within the limits of small number of stanzas. John Keats's ballad La Belle Dame sans Merci is an excellent example in this regard.

Ballad is the structure of poem Robin Hood and the Scotchman because it has stanza with four lines in rhythmic scheme.