The phrase Queensberry rules, also Marquis of Queensberry (rules), denotes the standard rules of boxing, originally drawn up in 1867 to govern the sport in Great Britain, named after John Sholto Douglas (1844-1900), 8^th Marquess of Queensberry, who supervised the preparation of the rules.

The earliest occurrence of the phrase that I have found is from this advertisement, published in The Dundee Courier and Argus (Dundee, Angus, Scotland) of Wednesday 26^th June 1872:

PERTH.
BY KIND PERMISSION OF THE
LORD PROVOST AND MAGISTRATES
OF THE CITY.
A GRAND HIGHLAND GATHERING and
ATHLETIC COMPETITION will take place on
SATURDAY NEXT, JUNE 29th,
On the SOUTH INCH,
Near the Princes Street Station.

When Prizes in Specie, Medals, Cups, &c., &c., amounting to upwards of £50, will be Competed for in Running, Leaping. Dancing, Piping; Sparring, “Professionals and Amateurs”; Vaulting, Great Five Mile Foot Race, &c., &c.,
All the best Sparrers in Scotland and some of the best English will compete for a Champion Cup. Marquis of Queensberry Rules.
Entries taken on the Ground by A. C. Campbell, Sec.
Sports commence at 3 o’clock. Admission, 6d.; under twelve, half price.
N.B.—Parties in Dundee wishing a Programme can get one of Mr Lamb, Bill Poster, near Courier and Argus Office.

In figurative use, Queensberry rules denotes the standard rules of polite or acceptable behaviour.

The Irish playwright, critic, polemicist and political activist George Bernard Shaw (1856-1950) used the phrase figuratively in the review of Romeo and Juliet, produced at the Lyceum Theatre on Saturday 21^st September 1895—review published in The Saturday Review of Politics, Literature, Science and Art (London, England) of Saturday 28^th September 1895:

The duel scene has none of the murderous excitement which is the whole dramatic point of it: it is tamed down to a mere formal pretext for the banishment of Romeo. Mr. Forbes Robertson has evidently no sympathy with Shakespeare’s love of a shindy: you see his love of law and order coming out in his stage management of the fighting scenes. Nobody is allowed to enjoy the scrimmage: Capulet and Montague are silenced; and the spectators of the duel are women—I should say ladies—who look intensely shocked to see gentlemen of position so grossly forgetting themselves. Mr. Forbes Robertson himself fights with unconcealed repugnance: he makes you feel that to do it in that disorderly way, without seconds, without a doctor, showing temper about it, and actually calling his adversary names, jars unspeakably on him. Far otherwise have we seen him as Orlando wrestling with Charles. But there the contest was in the presence of a court, with measured ground and due formality—under Queensberry rules, so to speak.