Revisiting Permissionlessness

While permissionless systems are theoretically open to all participants who adhere to predefined rules, in practice, then, they may still evolve into environments where only well-funded entities can meaningfully engage in consensus and governance. Despite the absence of explicit barriers to entry, practical constraints—such as the economic cost of staking or mining—can thus create an implicit form of exclusivity.

De-jure vs De-facto

As a result, the traditional binary classification of "permissioned" vs. "permissionless" systems may be insufficient to fully capture the nuances of decentralized networks. Instead, it may be more useful to distinguish between systems that are de jure permissionless—meaning that their formal rules do not impose restrictions on who can participate—and those that are de facto permissionless, where, in practice, participation is truly open, with no significant financial or structural barriers that privilege certain actors over others.

Building on this refined distinction between permissioned and permissionless systems, we can map these categories onto a 2x2 matrix to better illustrate how Sybil resistance mechanisms function both in theory and in practice:

	De Facto Permissionless	De Facto Permissioned
	(Open in Practice)	(Restricted in Practice)
De Jure Permissionless (Rules allow anyone to participate)	Truly Permissionless Systems: These networks are permissionless both in principle and in practice. Anyone can participate in consensus and governance without significant barriers.	Oligarchic Permissionless Systems: While the rules do not formally restrict participation, practical barriers—such as high staking requirements or expensive hardware—limit participation to a privileged few.
De Jure Permissioned (Rules restrict participation)	(This quadrant is empty because permissioned systems, by definition, cannot be permissionless in practice.)	Strictly Permissioned Systems: Participation is restricted by rules, and governance is controlled either by a group (Consortium Blockchains) or a single entity.