What are rules on loan players in Champions League?

What the report says

BBC Sport explains that UEFA Champions League rules allow loan players to face their parent clubs, unlike the loan restrictions used in some domestic competitions. The immediate example is Arsenal teenager Ethan Nwaneri, who is on a season-long loan at Borussia Dortmund and could play against Arsenal when the clubs meet in the league phase on Tuesday, 24 November.

The report says Nwaneri is one of 12 players in this season’s Champions League who are on loan between clubs in the competition. Of those, three were initially in line to face their parent clubs, though that number could increase if teams meet in later rounds. Two have already done so: Lutsharel Geertruida played for PSV Eindhoven against RB Leipzig, while Robert Ljubicic featured for Lask against AEK Athens.

BBC Sport notes that this is not a new practice. UEFA has long permitted loaned players to appear against the clubs they are temporarily leaving, and the article points to previous high-profile examples such as Fernando Morientes for Monaco against Real Madrid in 2004 and Thibaut Courtois for Atletico Madrid against Chelsea in 2014. The piece helps clarify why such matchups are allowed and why they can draw attention when clubs linked by loan deals meet in European competition.