Hull say they will have no objection to fans bringing rainbow flags to their next home game, which will be Israel Folau's first Super League match in England.
It follows claims from Castleford supporters that they were asked to remove flags supporting the LGBT movement after displaying them at Stade Gilbert Brutus, where Folau made his debut for Catalans Dragons on Saturday evening.
Folau, who was sacked by Rugby Australia last May for making homophobic comments on social media, is due to make his second appearance when the Dragons visit the KCOM Stadium on Sunday, March 1.
Catalans have said they do not have a policy of banning flags and promised to look into the matter while a Hull spokesman said: "We have nothing against pride flags in general."
The signing of Folau has been widely condemned by both Super League and the Rugby Football League, who says it was powerless to prevent his registration.
Wigan have called the visit of the Catalans in March "Pride Day" and Wakefield had invited LGBT groups to their game against the Dragons last Sunday before it was postponed.
Alison Grey, a Castleford fan, posted on social media during Saturday's game that she was asked to take down a rainbow flag.
She tweeted: "Just been told I am not allowed this flag because the club does not allow it. How disgusting."
She later said in an interview with Sky Sports: "We were asked if we could take the flag down, first because it was against health and safety. When we said that there were other flags around the ground they gave up.
"They then came back to us later on and said it was against the views of the club to have the flags."
Catalans coach Steve McNamara would not be drawn on the matter in his post-match press conference.
The former England boss said: "I am here to talk about football, not political or religious views or whatever else it might be. I am here to talk about rugby league. That is what I know, that is what I do, not any of the other stuff."
A joint statement from Super League and the RFL said: "Everyone should have the right to respectfully express their views.
"We are investigating. We will receive a full report by the end of this weekend and have more details by Monday."
