How can claimants assign periodic payments when the insurance company says that they are not assignable?
The annuity itself is not assignable because you do not own the annuity. The life insurance company, or a subsidiary thereof, that issued the annuity, typically owns it. Therefore, since you do not own the annuity, you cannot assign it. What you do own, and therefore can assign, is the right to receive periodic payments due under the release and settlement agreement. That is an absolute property right you have under the settlement agreement – it is your right to receive the periodic payments that you may assign in exchange for a lump sum payment.