Why can’t I enroll CRP that is still under contract?

If your CRP is still under contract, the view of the carbon market is that the soil carbon is already secured by virtue of the CRP enrollment (which prohibits plowing). Therefore, purchasing carbon rights on current CRP acres would not provide any additional benefits beyond those afforded by the CRP contract. However, the carbon remaining in grassland after the CRP contract expires could be plowed, and therefore purchasing the carbon rights to avoid the loss of that soil organic matter provides additional benefits.