Book of Vile Darkness (121-122):
A select choice of abilities of the Ruby Rod is usable at will by Asmodeus, but only once by anyone else. The wielder can cast Bodak Birth as if cast by a 20th-level spellcaster.
Bodak Birth (Book of Vile Darkness 86)
The caster transforms one willing subject [...] into a bodak. [...]
anyone that holds the figurine can attempt to mentally communicate and
control the bodak, but the creature resists such control with a
successful Will saving throw. If the bodak fails, it must obey the
holder of the figurine, but it gains a new saving throw every day to
break the control. If the figurine is destroyed, the bodak
Demand Submission (Book of Vile Darkness 165) is an ability by Asmodeus, not tied to the ruby rod:
If the creature fails, it submits [...] to the ruler of hell[...]
doing whatever Asmodeau asks as if every request of his was a
suggestion spell against which the target cannot resist
Guide to Hell (51)
His avatars all carry a ruby rod, a badge of office that inspires
instant obedience from any devil.
Fiendish Codex II: Tyrants of the Nine Hells (156):
Asmodeus sometimes bestows his ruby rod onto a particularly worthy
mortal to serve his ends.
Lore: The Ruby Rod is the symbol of office for the ruler of Nessus. He
who wields it rules Hell.
a wielder can activate any of its other special abilities once per
day. Asmodeus can use them at will, each as a swift action.
The Aura of Submission is notably an ability of Asmodeus, not of the ruby rod:
At the end of each of Asmodeus’s turns, creatures [...] saves or
submit to all of Asmodeus’s commands for 1 day, doing whatever he asks
as if every request of his was a suggestion spell against which the
target cannot resist. [...] A creature that successfully saves cannot
be affected by Asmodeus’s aura ever again.
The Nine Hells:
The devils of the Nine Hells are bound to obey the laws of their
superiors, but they rebel within their individual castes. Most
undertake any plot, no matter how foul, to advance themselves. At the
very top of the hierarchy is Asmodeus, who has yet to be bested. If he
were to be vanquished, the victor would rule the plane in turn. Such
is the law of the Nine Hells.
He can also assume other forms and is seldom seen without his
ruby-tipped scepter in hand.
Mordenkainen's Tome of Foes (9-10):
The ruby rod was given to Asmodeus by Primus of the modrons as part of the Blood war trial issued by the angels.
the true ruler of the Nine Hells is the immense body of rules and
regulations that dictate how all devils, even Asmodeus, must conduct
the Ruby Rod, that would guarantee his adherence to law. The artifact,
which has remained at Asmodeus's side ever since, grants him and his
underlings the right to enter in to contracts with mortals for their
souls but unleashes an inescapable punishment upon any devil that
breaches such a contract.
Editions in brackets after segments.
In the mentioned editions the ruby rod is a sign of office, but the power that creates submission is based on the order of hierarchy in the hells (2;3.0;3.5;5) and manifests in Asmodeus, not his ruby rod (2;3.0;3.5). While in 3.0 you can create a Bodak that has to obey unless it saves and then risks disintegration (3.0), there is no magical enforcement outside of that obedience and the obedience created by the ruby rod as a sign of the ruler of the hells (2;3.0;3.5;5). All Further suggestion or geas that can't be resisted are tied to Asmodeus (3.0;3.5).
A wielder can use the ruby rod and will receive obedience by any devils (2;3.0;3.5;5), but the ruby rod does not grant the power to create magical pacts that enforce the law (2;3.0;3.5;5). The wielder of the ruby rod is regarded as the ruler of the hells with its natural law and hierarchy (2;3.0;3.5;5).
The law of the hells is enforced by superiority, and thusly obedience is granted. Such is the law of the Nine Hells (2;3.0;3.5;5).
While the ruby rod is a sign of the office and any devils will obey the wielder, Asmodeus is still the undisputed ruler (2;3.0;3.5;5) who may grant the ruby rod to someone lower than himself, under his law of superiority (2;3.0;3.5;5).
And sometimes Asmodeus bestows his ruby rod onto a mortal to serve his ends (2;3.0;3.5). That mortal will see the obedience of devils (2;3.0;3.5;5).
The ruby rod itself can only punish the devils who breach their contracts with mortals (5). It grants them the right by the angels' trial, not the power (5).
The ruby rod grants Asmodeus and his underlings the right to enter into contracts with mortals, that his underlings have to be devils is not explicit. Whether the rod can extend its enforcement to none devils is also unclear (5). The laws of the hells regulate all devils and even Asmodeus (5).