 Block believes that people should have the legal right to sell themselves into slavery, or to buy and keep slaves, in a libertarian legal order.In an essay on "inalienability" of natural and legal rights, Block defends what he calls a "voluntary slave contract", arguing that it is "a bona fide contract where consideration crosses hands; when it is abrogated, theft occurs".He notes only Robert Nozick agrees with him, and critiques the views of the libertarians who disagree.