Christie and Arsenal's Kieran Tierney missed all three of Scotland's matches during the international break after being deemed close contacts of Southampton midfielder Stuart Armstrong, who tested positive for coronavirus.
However, according to Celtic boss Lennon, Arsenal has won its argument to have Tierney available to face Manchester City in the Premier League on Sunday (AEDT), while Christie remains unavailable.
"Our medical department have spoken to the (Arsenal) club doctor and they have been given the all-clear for Kieran to go ahead," Lennon said on Saturday (AEDT).
"So we have a fit and able player not being allowed to play which, if this scenario pans out that Kieran can play, we find that very confusing and we would want answers.
"Our preparations have been without Ryan. It would probably be folly to change that now but we would like to have him available for the squad if possible and what we are asking is, 'if it is OK for one, why is it not OK for the other?'"
Christie is one of four Celtic players likely to miss the game because of COVID-19. Odsonne Edouard, Nir Bitton and Hatem Elhamed also tested positive while away on international duty.
France Under-21 player Edouard's 10-day quarantine period is now over but Lennon admitted he had felt fatigued by the virus.
"He will be assessed today – we are going through that procedure at the minute, so we will know more later on this afternoon.
"He has been a bit tired and isolated but we will go through the tests and we will see how he is."
Saturday's clash between the Glasgow giants will be the first behind closed doors.
Both clubs have urged fans not to break regulations by mixing households or travelling to England to watch the game in pubs, with bars across Scotland's central belt currently closed.
"It is a huge ingredient that is going to be missing. The electricity, the atmosphere, the rawness, the noise, the colour," Lennon said.
"I think it is very difficult for this generation of players to go through what they are going through without supporters."
Rangers leads its rival by a point at the Scottish Professional Football League, but Celtic has a game in hand and is on an eight-game winning run in all competitions.
The pressure is therefore on Rangers manager Steven Gerrard to take advantage of Celtic's coronavirus misfortune.
But Gerrard believes the situation suffered by his side's rival is no different from an injury crisis he had to deal with before the international break.
"A lot of clubs are facing different challenges at the moment – Celtic obviously of late but it's pretty similar to the challenges we've faced for the last month you know, not having Joe Aribo, not having Kemar Roofe, missing Ryan Jack for three weeks.
"These things happen when you're managing squads of players and that's the reason why we try to build squads so we can cope in these situations."