Regulators

Fallout
Lead by the sadistic Caleb, the Regulators are a vicious gang that serves as the "police force" of Adytum in Southern California. Nominally under the authority of Adytum's mayor, Jon Zimmerman, they in fact manipulate Zimmerman and control Adytum's affairs, ruling harshly, expropriating a good part of Adytum's industrial wealth for themselves, and enforcing forced labor on Adytum's citizens. To legitimate their authority, they have claimed that the Blades, a survivalist group to the north, are a threat, and frame them for crimes such as the murder of Jon Zimmerman's son.

Fallout 3
In the Capital Wasteland, the Regulators are a group of self-appointed lawmen who wear cowboy style hats and dusters after the fashion of gunslingers and operate out of a farmhouse. If the player has the Lawbringer perk, he/she can trade fingers taken from the corpses of evil humans killed by the player, for good karma and Bottlecaps. The Regulators will also attempt to claim the bounty on the player's head if he or she commits serious crimes.

Regulators wear Regulator Dusters, and seem to have a fondness for laser weapons (laser pistols and laser rifles). In terms of durability and combat challenge, they're about equal to a Talon Company Merc.

The player may also discover the body of a dead Regulator, who, apart from providing a Regulator Duster, will have details on a named bounty and their last known location. (However, you'll want to search any buildings in the immediate area where you find the dead Regulator - a Regulator found in Arlington National Cemetery had a warrant for Junders Plunkett that placed him at Canterbury Commons, but he was instead hiding inside Arlington House.) If you have the Lawbringer perk, the finger of a named target is worth 1000 caps.

There is a bug where a player can pick-pocket a regulator, and he/she will have a named bounty for the player on them, even if the player is completely good.

This may be bugged, as you can retrieve both a normal finger and a named finger from the same target, then turn both in to Sonora Cruz at Regulator HQ for the normal and special bounties. The named finger remains in your inventory.

If a Regulator at HQ is successfully pickpocketed by a Good player possessing the Lawgiver perk, a Bounty notice for your character can be taken.

Note that the Regulators will target you if your Karma ever goes to "evil". Even if your karma dips to evil (i.e. if you enslave a few Raiders using the Mesmetron), and you quickly get it back up to "good" (i.e. by giving purified water to beggers) without encountering the Regulators, you will eventually encounter hostile Regulators even as a "good" character. Sometimes, Regulators and Talon Company Mercs will even appear together in the same squad to fight you!

Appearances in games
The Regulators appear in the original Fallout and in Fallout 3.