British clubs had seen a request to air the new anthem rejected following the death of Queen Elizabeth II, although the Scottish side played it nonetheless while also unveiling a huge display in honour of the late monarch.
“The incident you refer to is not the subject of any UEFA disciplinary proceedings,” said a Uefa spokesperson.
Wednesday night’s game only went ahead after Napoli fans were banned from attending due to a shortage of police numbers, while it was also moved back a day. The Italians claimed a 3-0 win at Ibrox.
Rangers hero Ally McCoist hailed the fans’ display, telling talkSPORT: “If that’s breaking the rules, I would actively encourage it. It was fantastic.
“It wasn’t even good, it wasn’t even brilliant, what a show of unity for the country – it was amazing. The Rangers supporters, a group of lads called the Union Bears, put on a Union Jack, honestly…
“I’ve got to say, the Napoli players were fantastic round the centre circle and the national anthem was sung by everybody in the stadium. It was actually heartwarming, honestly, to see all the unity from supporters and players alike.”
Meanwhile, Glasgow rivals Celtic are braced for a Uefa charged after proceedings were opened against a banner in the away end of their draw against Shakhtar Donetsk, which read “f*** the crown”.
“Please be informed that proceedings having been opened against Celtic regarding a banner," the organisation added. “The Uefa disciplinary bodies will decided on the matter in due course.”