Defence Regulations were emergency regulations passed between the lead-up and end of WW2, providing 
emergency powers to prosecute the war. Two 
Acts of Parliament were passed as 
enabling legislation to allow the Defence Regulations to be promulgated. 1) The 
Emergency Powers (Defence) Act 1939 was passed immediately before war was declared. 2) The 
Emergency Powers (Defence) Act 1940 was passed in the aftermath of the German attack on 
France in 1940. The 1940 Act allowed Defence Regulations to be made on matters such as 
industrial conscription.
The main Defence Regulations were the 
Defence (General) Regulations 1939, which were amended at various points throughout the war. Other Defence Regulations covered narrower fields of life. These included 
Defence Regulation 18B, which provided a framework for 
internment. 18B allowed the 
internment of people 
suspected of being 
Nazi sympathisers. The effect of 18B was to 
suspend the right of affected individuals to 
habeas corpus.
The Defence Regulations were 
Orders in Council and could amend any primary or secondary legislation within the limits of the enabling Acts to allow the effective prosecution of the war.
Originally the regulations did not create any 
capital offences, since the law of 
treason was thought to be sufficient. Defence Regulation 2A provided that "If, with intent to assist the enemy, any person does any act which is likely to assist the enemy or to prejudice the public safety, the defence of the realm or the efficient prosecution of the war, he shall be liable to penal servitude for life."
However, in 
1940 amendments to the regulations created 
two capital offences: 
"forcing safeguards" (breaking through roadblocks etc.) under regulation 
1B, and 
looting under regulation 38A. A 
third new capital offence, called treachery, was created soon afterwards by the 
Treachery Act 1940.
Since the emergency conditions created by the war persisted after the conflict was over, 
the last of the Defence Regulations, mainly those on 
food rationing, were 
not abolished until the early 1950s.
https://en.wikipedia.org/wiki/Defence_Regulations .
https://en.wikipedia.org/wiki/Defence_Regulation_18B .
https://en.wikipedia.org/wiki/Capital_punishment_in_the_United_Kingdom .