as I read it the question posed was 'WHich law do we follow?'
not what Daves or our reaction should be. It seems to me that if he is unable to do the work as he should he should not work there.

the question arises often: in canada the requirement to wear a helmet on a motorcycle the law conflicted with the some cultures rights to wear a turban. In the end the turban won out. (Which also applied to headgear for police officers - and now you may encounter police officers with turbans, or long braids (First Nation style).

this issue also came up when a Cab drivers convention wanted to rent a hall (a Legion hall) and were told they had to remove their headgear (as the Legion members are required out of tradition and respect for fallen comrades to remove their headgear when they enter
a hall) which ones religion takes precedence?

But there are other times where it is unclear, namely if ones
religion requires one to carry a weapon. (which may conflict with
local laws, ie. carrying weapons aboard an airplane, or into a courtroom). The Sikh religion requires that members wear a turban,
and carry a sword (among other things). I believe now the sword
is usually a small ceremonial sword - but not sure of the size or
effectiveness. In a BC court case a few years ago, the 'sword' fact came up and the Judge in the case mentioned that he hoped that no one is armed in the courtroom - as it is illegal to carry weapons into court.
(a few people in the courtroom got upset over it and cried racism).