Atletico president Enrique Cerezo claimed this week that Courtois, who is on loan in La Liga from Chelsea, would not play against his parent club should the teams be drawn together in the semi-finals.
The decision is said to have come from reports that the Spanish outfit would need to pay Chelsea a fee in order to play the 21-year-old shot-stopper.
In response to the reports, UEFA released a statement saying: "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.
"Furthermore, any attempt to enforce such a provision would be a clear violation of both the UEFA Champions League and the UEFA Disciplinary Regulations and would therefore be sanctioned accordingly."
Chelsea, Atletico, Real Madrid and Bayern Munich are all in the hat for Friday's semi-final draw in Nyon, Switzerland.