Number of Stories Written About 'Legalized' Murder?

Are you looking for stories like "someone needed killin'?"

Something like the end of Roadhouse where a bunch of people shot the antagonist, so no one person could be charged?

It was a thing in Rome to declare someone dead and then anyone who wanted to kill them and could manage to do so would be unprosecuted. AFAIK it was only used in high profile individuals

Logan's Run by William F Nolan (although the film of the same name is better known)
Unwind by Neal Shusterman
Battle Royale by Koushun Takami

Then of course there is Hitler and Cambodia.

Ira Levin's This Perfect Day and The Boys From Brazil. Different books, very different worlds/schemes, both I think what you're looking for though.

Yah, I understand, hence the two different types of community killin'.

Legalized killin', eh? This thread sparked a memory . . .

I wrote a draft about a post-apocalyptic society that developed a simple system of justice. In the absence of prisons, anyone convicted of a crime would be declared outlaw and banished from the realm for a specified period of time, and possibly required to make some form of restitution before reintegration in that realm's society.

If an outlaw were to illegally return to the realm during the period of banishment, any citizen of the realm could take the outlaw's head and claim a bounty commensurate with a sliding scale reward system. While not strongly encouraged, an outlaw could be hunted outside the realm during the period of banishment, but a head taken outside the realm would merit a proportionately reduced amount of reward. This society did not have the financial burden of a prison system. Instead, it developed a potentially lucrative and self-supporting industry of bounty-hunting, open to all who would chose such a career/lifestyle.

A hunter who was very good could become very wealthy. However, the big problem for the bounty hunter was rather significant. A bounty hunter was not allowed to make a mistake; take the wrong head--be declared an outlaw . . . Or even worse, be framed by a jealous rival with an agenda for taking the wrong head . . .

There's also Soylent Green (movie), and is probably more overpopulation/legalized suicide (plus another twist), which is loosely based on a book that actually included nothing about that, hence the "loosely".

You might want to research the true story of Ken Rex McElroy, of Skidmore, Missouri. A famous case of a really vicious and dangerous small-town bully who was ultimately murdered by a townsperson, in broad daylight, with dozens of witnesses, and nobody ever identified the killer (or killers, might have been more than one). Nobody saw nuthin. And everybody was happy McElroy was gone. There was a pretty good fictional (but factually accurate) TV movie made about this incident, In Broad Daylight, starring some big-name actors: Brian Dennehy, Cloris Leachman and Chris Cooper.

caw

If you count state execution as legalised murder(and why wouldn't you?), you might want to read up on a chap called Albert Pierrepoint, who was Britain's last official executioner.

Wiki for a starting point: https://en.wikipedia.org/wiki/Albert_Pierrepoint

There's a film about him too, although I haven't seen it so don't know if it's any good or not: https://www.rottentomatoes.com/m/pierrepoint_the_last_hangman/