Citizen’s arrests are authorized under state law rather than federal. One exception may be in Title 18, Section 2236 due to poor wording that includes the phrase “any person”.
State laws, of course, vary. In Texas, if memory serves, a citizen can make an arrest of a person if the citizen observes a felony crime being committed in his or her presence by the person being arrested. However, the felony must be serious enough to mandate a minimum of a one-year sentence. Unless you know law very well, it would be hard to make that assessment at the time.
This would give a person reasonable latitude if for example, you witness an armed robbery, aggravated assault (usually this means with a deadly weapon), or capital murder.
Of course, the law is a lot more subjective than a lot of people imagine or wish were the case. In some places, the district attorneys and law enforcement might pin a medal on a person for bravery, while in another jurisdiction the same act might bring down the full wrath of the law resulting in long-term incarceration.
Bottom line though, you cannot lawfully go “arrest” criminal judges and legislators.
But when a soft coup or silent war goes hot, ordinary laws do not apply any longer.
There's no such thing in my state anymore. No more death penalty = no capital murder.