Section 21 | Discrimination by vocational organisations.
From legislation.gov.uk
It shall be unlawful for a vocational organisation to discriminate against a person who is employed or is seeking employment in Northern Ireland, or who is engaged or is seeking to become engaged in an occupation in Northern Ireland,—
(a)where that person is not a member of the organisation—
(i)by refusing or deliberately omitting to accept his application for membership, or
(ii)in the terms on which it is prepared to admit him to membership; or
(b)where that person is a member of the organisation—
(i)in the way it affords him access to benefits or by refusing or deliberately omitting to afford him access to them, or
(ii)by depriving him of membership, or varying the terms on which he is a member, or
(iii)by subjecting him to any other detriment.