In a statement Uefa said: "In response to media reports referring to the situation of Club Atlético de Madrid goalkeeper Thibaut Courtois, Uefa would like to reiterate its position.
"Both the Uefa Champions League and the Uefa Disciplinary Regulations contain clear provisions which strictly forbid any club to exert, or attempt to exert, any influence whatsoever over the players that another club may (or may not) field in a match.
"It follows that any provision in a private contract between clubs which might function in such a way as to influence who a club fields in a match is null, void and unenforceable so far as Uefa is concerned."