Is it? I suppose this will vary depending on which country we're talking about, but as far as i know there's nothing in the US that makes it illegal to discriminate based on caste unless the determination of caste overlaps with another -ism, like race.
Not a lawyer, but as I recall there's case law suggesting that the US laws on ethnic or national origin and religion in practice are a protection against caste discrimination
Is it? I suppose this will vary depending on which country we're talking about, but as far as i know there's nothing in the US that makes it illegal to discriminate based on caste unless the determination of caste overlaps with another -ism, like race.