If you buy eggs from a shop, I'd say there is a fair chance that the animals are not treated that well.
EDIT: I now realize many others have already made this point in other comments, oopsie.
-Maximum of 3000 chickens in a flock and a maximum of 6 chickens per square meter in the coops, which must allow daylight in.
-The chickens must have access to perches and nests.
-At least one third of the flooring must be loose bedding, such as straw or sand, to allow the chickens to dust bathe.
-The chickens must have all-year access to outdoor areas with at least 4 square meters per chicken. It must be covered by grass or other vegetation, and must provide shelter from wind/weather. An outdoor area must stand unused every other year, for parasite prevention and to let the vegetation regrow.
-Beak trimming is prohibited.
-Feed must be organic and must include roughage.
While it's not perfect, it's a damn sight better than battery caged hens.
Under the HFAC standard, antibiotics are forbidden, mammalian proteins in feeds are forbidden, beak trimming has strict guidelines, etc.
Note that HFAC paradoxically/disappointingly doesn't require chickens to be have range, but if the package says free range, there's a 108 sq.ft.-per-bird requirement. Pete and Gerry's eggs are marked free-range.