Short answer? I don't know if it works overseas, but I have become quite acquainted with the law here in the US. I don't see why it wouldn't apply elsewhere.

A cut and paste from one of the sources I used in my letter:

The EEOC and courts have consistently found that Title VII defines religion very broadly to include not only traditional, organized religions such as Christianity, Judaism, Islam, Hinduism, and Buddhism, but also religious beliefs that are new, uncommon, not part of a formal church or sect, only subscribed to by a small number of people, or that seem illogical or unreasonable to others. Moreover, an employee’s belief or practice can be treated as “religious” under Title VII even if the employee is affiliated with a religious group that does not espouse or recognize that individual’s belief or practice, or if few — or no — other people adhere to it.

Importantly, while social, political, or economic philosophies, as well as mere personal preferences, are not “religious” beliefs protected by Title VII, the EEOC and some courts have taken the position that certain non-theistic moral or ethical beliefs may qualify as “religious,” provided they are sincerely held with the strength of traditional religious views. For instance, at least one court has declined to dismiss a Title VII religious accommodation claim brought by a vegan who refused to comply with her employer’s mandatory flu vaccine policy on the grounds that the vaccine contained and/or was produced using animal by-products. On the other hand, it does not appear that any court to date has extended such protection to those who adhere to the growing anti-vaccination movement.