Dimensional Lock

You create a field that completely blocks bodily extradimensional travel. Forms of movement barred include Astral Projection, Blink, Dimensional Door, Ethereal Jaunt, Etherealness, Gate, Maze, Phasing, Plane Shift, Shadow Walk, Teleport, and similar spell-like or psionic abilities. The Dimensional Lock does not interfere with the movement of creatures already in ethereal or astral form when the spell is cast, nor does it block extradimensional perception or attack forms such as a basilisk's gaze. Dimensional Lock does not prevent summoned creatures from disappearing at the end of the summoning spell.

Once the spell is in place, however, extradimensional travel into or out of the affected area is not possible.