The Belgium international is currently in his third season on loan at Atletico Madrid, who have been drawn to face Chelsea in the semi-final of Europe's premier club competition.
Reports had suggested Atletico would be required to pay a fee in order for Courtois to feature against Chelsea, due to the terms of his loan deal.
However, UEFA released a statement prior to the semi-final draw, reiterating their stance that such a clause would be classed as "null, void and unenforceable".
Gourlay insists there was never going to be an issue with Courtois playing in the two-legged tie.
"The loan was arranged back at the start of the season. Thibaut can play, that was never in doubt," he told Sky Sports.
"Regarding the UEFA statement, we'll evaluate that in due course. As far as Chelsea is concerned we've complied with loan rules.
"Thibaut can play against Chelsea if selected by the Atletico Madrid manager. That is fact."
After their dramatic progression on away goals against Paris Saint-Germain, Jose Mourinho's men remain in the hunt for European and domestic glory.
While Gourlay was respectful of Diego Simeone's La Liga leaders, he expressed pleasure at the direction Chelsea are heading in.
"They (Atletico) are a fantastic side but so are the other teams in the last four. It sets us up for two fantastic games," he added.
"What we need to do is be totally prepared but we've got some important games to come before that.
"If somebody had said to me at the start of the season that with five weeks to go we'd be in the semi-final of the Champions League and in the (Premier League) title shake-up I'd take it.
"This is what we work for and we'll take one game at a time and see where we go.
"We're definitely heading in the right direction so we're in a good position. Everyone has done fantastically well and our 12th man was the fans against PSG."
