Unless the nature of the matter or a prescript of law establishes otherwise, a person is able to exercise executive power over his subjects, even when he or they are outside his territory; he is also able to exercise this power over travelers actually present in the territory if it concerns granting favors or executing universal laws or particular laws which bind them according to the norm of can. 13, §2, n. 2.
Source: Code of Canon Law (Vatican.va)