I feel that your point on interpretation is somewhat overstated. Anything, really, could be claimed to be a matter of interpretation, but to be sensible we must set limits where we say that A is objectively true whilst B is objectively false. I do not doubt that somewhere someone is wearing pink plimsolls all day long claiming it to be a central tenant of Christianity, but to have a reasoned discussion we must discard the fringe beliefs of the loonies, nutters and extremists. Science tells us that a high percentage of our ability to be properly understood, and certainly empathised with, when we talk comes from non-verbal cues. By covering the face we are removing these cues and thus, objectively, we are materially reducing our ability to communicate with others. Is it necessary to communicate with others? Clearly this must be answered in the affirmative; few activities that warrant going outside do not involve, to some extent, communication with others. So proper communication is necessary and this is only achieved through the full gamut of muscular movements available to the face. The face remaining uncovered is thus necessary. I believe this to be relatively objective and, as such, not subject to interpretation. Firstly, I would challenge the concept that many wear the niqab believing it to be a requirement of their faith. When saying it is religious, what they perhaps mean is that they are using it to solve the religious necessity to cover their hair. In that sense the niqab can answer that religious need, however, just as a computer does far more than allowing me to write a letter, the niqab also fulfils their cultural needs. As such, it is a cultural item that happens to also fulfil a religious need - just as a long tunic, for a man, would fulfil the needs of his religion - to be properly covered - but also, mostly, fulfils his cultural needs to have something, which he considers 'good looking'. One would not consider that tunic to be a religious item, but rather a cultural one. In any case, the fact that some people wear an item erroneously believing it to be a part of their faith does not make it a religious item, it simply makes them wrong. To take the pink plimsolls as an example again - if I was to wear them then would they be a religious item? No, they would be pink plimsolls. For something to be a religious item it is not good enough for someone to simply declare that they are - there must be something in their religious texts stating they are - otherwise their belief is unfounded.