Part 2: Lawful interception of communications Chapter 1: Interception and examination with a warrant Section 20: Grounds on which warrants may be issued by Secretary of State
Subsection (2) sets out the grounds on which a warrant may be issued by the Secretary of State. These are: in the interests of national security, for the purpose of preventing or detecting serious crime, in the interests of the economic well-being of the United Kingdom (in circumstances relevant to the interests of national security), or for giving effect to the provisions of a mutual assistance agreement. Subsection (4) makes clear that a warrant may only be considered necessary in the interests of the economic well-being of the UK when it relates to the acts or intentions of persons outside the British Islands.
	Subsections (5) and (6) specify circumstances in which a warrant may not be considered necessary. A warrant cannot be considered necessary if its only purpose is gathering evidence for use in legal proceedings, or only on the basis that the information that would be obtained relates to trade union activity in the British Islands.