legal instrument

document which creates legal relationships or attests to them; document used as a law

Legal instrument is a legal term of art that is used for any written legal document such as a certificate, a deed, a will, an Act of Parliament or a law passed by a competent legislative body in municipal (domestic) or international law. Many legal instruments were written under seal by affixing a wax or paper seal to the document in evidence of its legal execution and authenticity (this could often remove the need for consideration in contract law); however, today most jurisdictions have done away with the requirement of documents being under seal in order to give them legal effect.
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Noun
1. (law) a document that states some contractual relationship or grants some right
(synonym) legal document, official document, instrument
(hypernym) document, written document, papers
(hyponym) derivative instrument, derivative
(classification) law, jurisprudence