Consult canon 13:
§1. Particular laws are not presumed to be personal but territorial, unless it is otherwise evident.
§2. Travelers are not bound: 1) by the particular laws of their own territory as long as they are absent from it unless either the transgression of those laws causes harm in their own territory or the laws are personal; 2) by the laws of the territory in which they are present, with the exception of those laws which provide for public order, which determine the formalities of acts, or which regard immovable goods located in the territory.
Travelers are bound to universal laws, of course. Since a Catholic is ascribed to the Latin Church or one of the Eastern Churches, he or she would be bound to those universal laws of that Church.
They would also be generally bound to any personal precepts. (For example, a bishop may forbid his clergy to enter gam(bl)ing casinos anywhere. The precept “sticks to the bones,” regardless of where they are.)
Otherwise, they would not be bound to the particular law of their own diocese. (For example, the bishop establishes a holy day of obligation as a general law. This is the particular law mentioned in the canon. His subjects are not obliged to observe the obligation outside the diocese, unless this would cause harm in that diocese of origin.)