There is no direct law, but derived from the freedom to practice religion part of the constitution with non-interference of the government.
What the legal luminaries have differed on is what constitutes a core religious practice, and that is where the ambiguity and disagreements arise.
If you recall recently there was a SC judgment on the right of a Muslim air force person who was discharged because he insisted on keeping a beard. The court had to first determine if keeping a beard was an essential part of faith.
I found this to be interesting, and love Gautam Bhatia's legal prowess. Read more at:
https://indconlawphil.wordpress.com...s-muslim-beard-judgment-a-missed-opportunity/