The two were spotted watching the Legends Football League (LFL) match at AAMI Park on Saturday, raising questions about the associations of the 105-game AFL forward.
Richmond chief executive Brendon Gale conceded the friendship was "disappointing" but the club was not likely to sanction King.
"In this situation we would expect Jake to make better decisions," Gale told Radio SEN.
"We don't offer directions or hard and fast rules to our players (on their associations)... we provide advice, we provide guidance but we expect them as adults to make their own decisions."
Gale said King "bumped into" Mitchell, a former Bandidos boss, at the event.
Following the Tigers' Round 20 win over Brisbane at the MCG, Mitchell was invited into the Richmond rooms by King, prompting the club to tell the player his association with the former bikie enforcer was unacceptable.
Calling on King to think "long and hard" about the long-standing friendship, Gale highlighted the Australian Crime Commission report in February this year which showed links between organised crime and professional sport.
"The contents talk about the connection between criminal identities and organised crime between human growth hormones... match-fixing, corruption, there's that risk," he said.
"Our players, like all players, have got to be very mindful of associating with those with a criminal past."
Gale called the media spotlight on King an instructive opportunity to remind the player of the risks involved.
The event was the LFL's first match in Melbourne, featuring scantily-clad women playing a modified version of gridiron, drawing more than 3000 people to AAMI Park.