Only if the arrest and sentence (which can include execution) is carried out by that agency charged with the protection of citizens' rights, ie the state. It's why government exists, and it's high time it did its primary and most essential job. There needs to be due process, otherwise we just live as savages.
If the killing is done by non-State actors, we descend into barbarism and the cycle of crime and violence is entrenched, not mitigated.
By due process, do you mean court proceedings? That will simply never work. There are are high ranking officials from regional police superintendents, to high-ranking customs officers, to mayors, to premiers to even the executive that are paid with drug money to look the other way. They cannot be brought down via the judicial system as very often they control the evidence chain.