The Gemara permits avid inish dina l’nafshei – a person can enforce his own rights himself in certain cases (Bava Kama 27b-28a; Rambam Hilchos Chovel uMazik 1:13; Shulchan Aruch CM 4:1). The classic trigger is when justice is obvious and waiting would cost him – like grabbing your own sefer back from someone reading it. How far does that reach today? Does the rule still work when there’s a functioning court system that can do it for you, or is that exactly when it shuts off? What counts as ‘I’d lose it otherwise’ – can I physically take back my own property, withhold a deposit, remove someone squatting on my land, without calling anyone? Does it extend past property at all? And does dina d’malchusa forbid self-enforcement even where the Torah allows it?