Flatus Veteranus
The Riot Act,1714 was repealed by the Statute Law (Repeals) Act, 1973. However, the common law right and duty of justices to suppress a riot at any moment with whatever degree of force may be necessary was not affected at that time.
My recollection from the late 60s is that the British Army was deployed to Northern Ireland in aid of the civil power, primarily because the Royal Ulster Constabulary had lost the confidence of the populace, and was unable to maintain law and order. Again, if memory serves me correctly, the Army relied initially on a common law power to suppress riots. However, over the years, various pieces of legislation were enacted to codify the Army's powers of riot suppression, arrest, questioning of suspects and detention.
Interestingly, in Oz, post September 11, 'treason' has been recently redefined in Federal legislation to allow the offence to be made out when a person assists another country or organisation engaged in armed hostilities against the Australian Defence Force, such as in Iraq. This came too late to 'catch' two Australians who had been captured by the US in Afghanistan and interned in Guantanamo Bay.
Part 5.1—Treason Division 80—Treason 80.1 Treason
(1)
A person commits an offence, called treason, if the person:
(a) causes the death of the Sovereign, the heir apparent of the Sovereign, the consort of the Sovereign, the Governor-General or the Prime Minister; or
(b) causes harm to the Sovereign, the Governor-General or the Prime Minister resulting in the death of the Sovereign, the Governor-General or the Prime Minister; or
(c) causes harm to the Sovereign, the Governor-General or the Prime Minister, or imprisons or restrains the Sovereign, the Governor-General or the Prime Minister; or
(d) levies war, or does any act preparatory to levying war, against the Commonwealth; or
(e) engages in conduct that assists by any means whatever, with intent to assist, an enemy:
(i) at war with the Commonwealth, whether or not the existence of a state of war has been declared; and
(ii) specified by Proclamation made for the purpose of this paragraph to be an enemy at war with the Commonwealth; or
(f) engages in conduct that assists by any means whatever, with intent to assist:
(i) another country; or
(ii) an organisation;
that is engaged in armed hostilities against the Australian Defence Force; or
(g) instigates a person who is not an Australian citizen to make an armed invasion of the Commonwealth or a Territory of the Commonwealth; or
(h) forms an intention to do any act referred to in a preceding paragraph and manifests that intention by an overt act.
Penalty: Imprisonment for life.