I see people wonder why the Church of Seiros would tolerate Abyss, especially the presence of criminals and religious dissidents. The answer to this one is relatively simple: Abyss is what is called a State of Exception.
A state of exception exists when a government deliberately creates an area of lawlessness, or more exactly, a place where the law is not applied in the same way as it has been historically/elsewhere. The people living within a state of exception live within exceptions to the law. Governments may have any number of motives to establish a state of exception. Bad motives include how a state of exception allows the government to violate its own laws/use more violence than normal. Lawlessness can also be useful if members of the government have black market or other unethical interests (one of Aelfric’s motivations). Better reasons for a state of exception may be to respond to a crisis (states of emergency are sometimes states of exception) or to establish a refuge for people who cannot exist in normal society (Aelfric’s initial motivation and a reason to allow Abyss to survive post-Aelfric).
The theory of states of exception is largely developed by Giorgio Agamben. He points to Nazi Germany and Guantanamo Bay as real-life examples. I was exposed to the concept by Jason de León’s book The Land of Open Graves, where he argues that the US-Mexico border is a state of exception.
The key to a state of exception is that the condition of lawlessness is a deliberate creation of the state itself. This makes it different from a region where the law is absent or has lost control (as often occurs in border regions, colonies, and the like). Looking at Abyss, the specific principles in suspense are: the supremacy of the aristocracy, the supremacy of the church, and general penal law. The aristocracy and church do not assert their power over the Abyssians (the aristocracy cannot assert its power, while the church can assert its power if it so desires, but generally does not).
Other examples in Fire Emblem include the various nations seized by cults (Nohr under Iago, Plegia, Rigel under the Duma cult). Nonexamples include western and southwestern Zofia (overrun by pirates and bandits, not government-created), the Ylisse side of the Ylisse-Plegia border before the Shepherds stabilize the region (the instability is created by an enemy state, not the state itself), and Ylisse in Lucina’s timeline (assuming Grima did not somehow become the head of state and legally enforce his destruction). Valla strikes me more as a failed state rather than a state of exception (it definitely has some state of exception kind of stuff going on, but we don’t really see if Vallan law has survived in any way past whatever Anankos orders in the moment).
[Originally for r/fireemblem]