As paraphrased by a federal judge in Richmond:
Title VII’s treatment of religion has been said to constitute a special category of discrimination. This is because the statute defines religion to include all aspects of religious observance and practice, as well as belief, unless an employer demonstrates that he is unable to reasonably accommodate an employee’s religious observance and practice without undue hardship on the conduct of the employer’s business. Thus, an employee is not limited to the disparate treatment theory to establish a discrimination claim. An employee can also bring suit based on the theory that the employer discriminated against him by failing to accommodate his religious conduct. Unique to cases involving religious discrimination, as opposed to race or sex discrimination, such a theory permits recovery without regard to how the employer treated other protected (or unprotected) employees.
Religious discrimination may be one of the thorniest aspects of Title VII, and a major stumbling block with lots of opportunities for mistakes. So make sure you’re treading carefully.