Would it be to counter something like the clay golems 'cursed wounds', that don't heal naturally?
Would regenerate heal cursed wounds? as an (Ex) ability it is probably closer to natural healing than magical.
Cursed Wound wrote:
Cursed Wound (Ex) The damage a clay golem deals doesn't heal naturally and resists magical healing. A character attempting to use magical healing on a creature damaged by a clay golem must succeed on a DC 26 caster level check, or the healing has no effect on the injured creature.