Israel Folau's Catalans Dragons club and the English Super League are investigating claims that spectators were told to remove rainbow flags during the controversial star's debut.
Last May, Folau was sacked by Rugby Australia for posting homophobic comments on social media, but joined Catalans last month.
The 30-year-old was impressive in his debut, scoring a try and helping the Dragons to a 36-18 win over the Castleford Tigers on Sunday (NZ time), but the match was overshadowed by the news that fans were told to remove the flags, a symbol of LGBT pride.
"Everybody should have the right to respectfully express their views," said the league. "We are investigating.
"We will have more information by Tuesday."
Castleford fan Alison Grey was one of those at Stade Gilbert Brutus in Perpignan with a rainbow flag, and she was first told the flag contravened health and safety, and then it was against club policy.
"Rugby league has said it's an inclusive sport," she told Australia's 7News. "It sells itself on being a family game in England.
"The problem is that he hasn't come out and apologised for what he said. He's left his social media posts up, so he has no remorse for what he's said."
A Dragons club official told 7News reporter Hugh Whitfeld that "another banner that was more aggressive was removed", but he considered the rainbow flag a symbol of peace and that was fine.
Fellow Super League club Hull FC said it have no objection to fans bringing rainbow flags to their next home game on March 2, which will also be Folau's first match in England.
"We have nothing against pride flags in general," said a Hull spokesperson.
The Wigan Warriors have called the visit of the Catalans in March 'Pride Day' and Wakefield had invited LGBT groups to its game against the Dragons last Sunday, before it was postponed.
Catalans coach Steve McNamara would not be drawn on the matter in his post-match press conference.
"I am here to talk about football, not political or religious views, or whatever else it might be," said the former NZ Warriors assistant coach.
"I am here to talk about rugby league. That is what I know, that is what I do, not any of the other stuff.
Former Silver Ferns netballer Maria Folau - wife of Israel - was at the match and happy to see her husband back out on the rugby field.
"We were extremely nervous about how today was going to go, but praise God," she told Nine News.
"I'm just so blessed that he was out there to play the game that he grew up loving and we're so blessed to have this opportunity to be here in the south of France."
Sunday's match was Folau's first outing since being sacked by Rugby Australia and his first rugby league game since 2010.