This sample resignation letter cites moving out of the country as a valid reason for quitting a job.
To our great excitement, my wife has secured a teaching position in (country), and our children and I will be joining her for the two-year term of her contract. This is an opportunity to broaden the world that Nick and Katie experience; we cannot pass this up.
Although XYZ Company has been extremely generous in regard to the mutually beneficial arrangement of telecommuting, the fact that my family and I will be located in such a remote location, with still-developing technology infrastructure, means that I would not be able to give the team the access and attention it deserves.
Please keep me in mind for any contract work in the future, especially if constant communication is not required for the duration of the project.