Sentence:  Subscriptions and donations to political parties are usually <WSD>disallowable</WSD> but in the case of Morgan v Tate and Lyle Ltd (1954) a political donation to the Conservative Party was allowed because it was made in order to resist the nationalisation of the sugar industry proposed by the Labour Party ... 
Meaning of the word marked with <WSD> tags:  Able to be disallowed.