An exercise of universal jurisdiction is where a State makes it a crime before their courts for anyone, anywhere to commit a certain act. With this in mind I found the following passage drily amusing:
"... in United Kingdom law universal jurisdiction is asserted in sections 47 and 51 of the Anti-Terrorism, Crime and Security Act 2001, in respect of the offence of knowingly causing a nuclear explosion without authorisation. The Rule of Law is a wonderous thing."
(See Vaughan Lowe's chapter on "Jurisdiction" in Evans (ed), International Law).