The Locality property of SLE says the following. Let be simply connected and agree with in a neighborhood of , and let be conformal with . The image under of an in , stopped when it first leaves , has the law of an in , up to the corresponding stopping time and a change of half-plane-capacity parameterization.
Explore the two stopped curves in the opposite order. Begin with an from to , stopped on leaving , and then, in its unbounded complementary component, draw an from to , stopped on leaving . Before their respective stopping times, each curve is separated from the neighborhood in which the other hull changes the domain. The Locality property of SLE therefore says that mapping out the other stopped hull does not change either stopped marginal law.
The two exploration orders consequently define the same joint law for the pair of stopped hulls. Disintegrating this joint law with respect to the second curve shows that, conditional on , the first curve is an in the unbounded component of
from to , stopped when it leaves , as required.
Choose a Möbius transformation of that fixes and exchanges with . By Conformal invariance of SLE, it transforms an from to into one from to . Until is disconnected from infinity, the discrepancy between the two target domains lies beyond the component visible from the growing tip. The Locality property of SLE therefore makes the two initial curve laws identical up to that disconnection time. Hence an from to , stopped at , has the law of an from to stopped when it disconnects from infinity.