An act is not protected if the reason, or one of the reasons, for which it is done is the fact or belief that a particular employer—
For the purposes of subsection (1)(b) an employer discriminates against a person if, but only if, he ensures that his conduct in relation to—
is different, in some or all cases, according to whether or not they are members of a trade union, and is more favourable to those who are.
An act is not protected if it constitutes, or is one of a number of acts which together constitute, an inducement or attempted inducement of a person—
References in this section to an employer employing a person are to a person acting in the capacity of the person for whom a worker works or normally works.
References in this section to not being a member of a trade union are to not being a member of any trade union, of a particular trade union or of one of a number of particular trade unions.