In a self-sale contract, you relinquish your labor rights for your working lifetime but retain your right to life, etc. Irreversibility isn’t unique to self-sale contracts. For instance, transferring material property is also irreversible, as the purchaser can transform it or refuse to sell it back. This argument doesn’t rule out self-sale in all cases. After a self-sale, the person can still buy themselves back. Inalienable rights actually rule out these abhorrent contracts.