Is the hijab so fundamental as to warrant excommunicating (considering as an infidel) the one who abandons it, especially in non-Muslim societies?

The hijab is an obligatory duty for believing women, and whoever abandons it commits a sin. However, she is not deemed an apostate for it. The proof for this is the Almighty's saying: "O Prophet, tell your wives and your daughters and the women of the believers to bring down over themselves [part] of their outer garments." The presence of a woman in a non-Muslim society does not exempt her from it; rather, it is a protection for her, and by it, her chastity is known, as the Almighty said: "That is more suitable that they should be known and not be abused. And ever is Allah Forgiving and Merciful." It is obligatory to adhere to it and to be patient with mockery, for in it there is elevation of ranks and an example for others.