CAMRA’s official definition of Real Ale is, "beer brewed from traditional ingredients, matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide." It's an awkward definition that, like Germany's Reinheitsgebot, can be quite restrictive. However, the term "traditional ingredients" is designed, like the Reinheitsgebot, to prevent artificial preservatives or cheap adjuncts or chemicals from being used in the making or storing of the beer.
Inserting "traditional ingredients" into the definition of craft would over the problem of chemicals.