Question with Steward of The Great Beyond and incomming teleports

[Sharker167]

"Whenever a creature attempts to use a teleportation effect or summon a creature within 30 feet of you, you may attempt to block the effect. Make an opposed caster level check (1d20 + caster level) as an immediate action. If the check succeeds, the spell or effect fails and is wasted; otherwise, it is unaffected. "

Is this saying that you can block an incoming teleport originating from outside of 30ft?

[Diego Rossi]

Y would say that it can block both inbound and outbound teleportation in the area of effect.

[Claxon]

My reading would be anyone teleporting into or out of the space within 30ft of you.