Carte-blanche

unconditional authority; full discretionary power: The government appears to have given the military carte blanche in Afghanistan.
She was given carte blanche to decorate her room as she wished, perhaps an unwise decision on the part of her parents.
Synonyms: license, free rein, blank check, free hand.
Cards. a hand having no face card but with a special scoring value, as in piquet.
Historical Examples

Mrs Langley, therefore, gave her carte-blanche to eat what she pleased.
The Pirate City R.M. Ballantyne

I wish you’d give me carte-blanche for all my patients, and all their wants.’
North and South Elizabeth Cleghorn Gaskell

I gave Charley carte-blanche to ask any of my Richmond acquaintances—and all for what?
Alone Marion Harland

“I give you carte-blanche as regards expenses,” said her ladyship with decision.
The Argosy Various

Her dainty drawing-rooms were curiously conventional—the natural result of carte-blanche to a fashionable upholsterer.
The Twelfth Hour Ada Leverson

You have drawn on me with carte-blanche liberties and spent fortunes like a prodigal!
The Law of Hemlock Mountain Hugh Lundsford

They recognized the faith that had commissioned her to speak as trustee, and to act with carte-blanche powers.
The Law of Hemlock Mountain Hugh Lundsford

noun (pl) cartes blanches (ˈkɑːts ˈblɑːntʃ; French) (kart blɑ̃ʃ)
complete discretion or authority: the government gave their negotiator carte blanche
(cards) a piquet hand containing no court cards: scoring ten points
n.

1707, blank paper, French, literally “white paper” (see card (n.) + blank (adj.)); figurative sense of “full discretionary power” is from 1766.
carte blanche [(kahrt blahnsh, kahrt blahnch)]

To be given “carte blanche” is to receive the power and authority to do as one wishes: “The prime minister herself did not take any action on the refugee issue but gave her minister of the interior carte blanche to deal with the situation.” Carte blanche is French for “blank card,” meaning one that can be filled in as a person wishes.