The Treason Act 1351 is an
Act of the
Parliament of England which codified and curtailed the common law offence of
treason. No new offences were created by the statute. It is one of the earliest English
statutes still in force, although it has been very significantly amended. It was extended to Ireland in 1495 and to Scotland in 1708. The Act was passed at
Westminster in the
Hilary term of 1351, in the 25th year of the reign of
Edward III and was entitled "A Declaration which Offences shall be adjudged Treason". It was passed to clarify precisely what was treason, as the definition under
common law had been expanded rapidly by the courts until its scope was controversially wide. The Act was last used to prosecute
William Joyce in 1945 for collaborating with Germany in
World War II.