Green’s Dictionary of Slang

(Irish) whisky on which duty has been paid, as opposed to contraband or home-distilled.

1818		R. Peel speech 30 May in Speeches of [...] Sir Robert Peel (1853) 106: The gallant general replied [...] ‘If the people could get any other, they would not drink parliament whisky.’.
1822		Mew Monthly Mag. IV 506: But there is another distinction, and that is between parliament whisky, and poteen, or whisky made in defiance of government and all its ordinances.
1829		Mirror of Lit. 73: If you are very ignorant, you must be told that poteen is the far famed liquor which the Irish, on the faith of the proverb, ‘stolen bread is sweetest’, prefer, in spite of law, and-no-not of lawgivers, they drink it themselves, to its unsuccessful rival, parliament whiskey.
1839		Museum of Foreign Lit. new ser. VIII 230/1: His Majesty had the good taste to forbid the appearance of excised or ‘Parliament whisky,’ at the royal table.
1851		(ref. to 1822) Dundee, Perth & Cupar Advertiser 3 Jan. 3/3: It got the name of ‘senatorial brandy,’ which will recall to recollection the ‘parliamentary whisky’ of 1822.
1866		Elgin Courier (Scot.) 16 Nov. 5/2: He prefers ‘British electoral gin to Irish Parliamentary whisky’.
1878		C. Tovey Wit . . . distilled from Bacchus 199: The Parliamentary Whisky (as they called the legal distillation).
1978		J. McGuffin In Praise of Poteen n.p.: One important result of this [introduction of new government regulations, 1780s] was that the quality of legal (or ‘parliament whiskey’ as it was called) declined as distilleries were forced to work faster and faster [BS].
2000		(con. c.1800) R. Mathieson Survival of the Unfittest 103: The local (or smuggled) product was cheaper and naturally thought to be much superior to the government-controlled ‘parliamentary’ whisky.