Retention Policy Designer allows you to protect a simple policy. When you protect a retention policy, you cannot modify or delete items that fall under that policy but you can accession them.
When you accession an item, you transfer the physical custody of that item to a new owner, such as an archival institution. Policies are not protected by default. Allow a policy to remain unprotected when you want to modify the keys or custom properties for items that fall under that policy.