Spanish term
darle carta de
Proposed translations
United States
Each translation a gem!
Native in: English (Variant: US) 
Works in: Spanish to English, Portuguese to English
endorse
[...] vigor de la Ley, una vez que el Gobierno apruebe la Orden Ministerial que debe desarrollarla y **dar carta de naturaleza** al mercado de mezclas directas de gasolina y bioetanol en España. abengoabioenergy.es
[...] law to become effective, which will occur when the government approves the Ministerial Order to enact it and to **endorse** a market for direct petrol and bioethanol mixtures in Spain. abengoabioenergy.es
United Kingdom
Flair and accuracy tailored to your text
Native in: English 
Works in: Spanish to English, German to English
give/lend status to
United States
PhD in Translation Studies
Native in: English (Variant: US)
Works in: Spanish to English, English to Spanish
acknowledge/recognize
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Note added at 5 hrs (2021-12-25 04:54:43 GMT)
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... involves acknowledging the legislative nature of the committee/commission created ...
Austria
Retd.T&I, Barrister & Austro-Advokat
Native in: English (Variants: British, Scottish)
Works in: Spanish to English, English to Spanish, French to English, and 5 more.
grant (such body) a charter of a legislative nature
I doubt the meaning is 'carte blanche'.
char·ter 1. a written grant by a country’s legislative or sovereign power, by which an institution such as a company, college, or city is created and its rights and privileges defined. ∎ a written constitution or description of an organization's fun
the policy sets out binding rules of general application, i.e., of a legislative nature, (such as rules of a regulatory body or provisions of a collective agreement) as opposed to those which are administrative in nature
United States
ES to EN, Latin and Spain to English US
Native in: English (Variants: US South, British, US)
Works in: Spanish to English, Spanish to Simple English, English, and 1 more.
darle carta de naturaleza legislativa
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Note added at 2 days 19 hrs (2021-12-27 18:55:50 GMT)
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giving a letter of a legislative nature
United Kingdom
experienced and well qualified linguist
Native in: English (Variant: UK)
Works in: Spanish to English, English, Spanish, and 3 more.
to grant legal status
'The initial stage, relative to the simplified formalities and procedures of an open government, incorporates the granting of legal status to a Committee formed by governmental agreements, in favour of administrative titles and simple procedures in a form which is available to the public. Such a policy has not yet been introduced by this government.'
ESP: 'En la etapa primera, relativo a las formalidades y procedimientos o trámites simplificados de un gobierno abierto, se incorpora la otorgación del estatuto legislativo a una comisión formada de un acuerdo gubernamental.
Está a favor de los títulos administrativos y los trámites sencillos de una forma disponible al público. Una dicha poliza todavía no está puesta en march por este gobierno.'
Discussion
It seems that the term "naturaleza" should have been part of your question.