The Rugby Players' Association (RPA) has questioned the Rugby Football Union's (RFU) misconduct charge for England fly-half Danny Cipriani.
The RPA argues that a "non-rugby" nightclub incident has already been dealt with "appropriately" by the courts and his club, Gloucester.
"We will be raising this directly with the Rugby Football Union," it said.
Cipriani, 30, faces a RFU hearing in front of an independent disciplinary panel in Bristol on Wednesday.
He has already been fined by both magistrates and Gloucester.
The former Wasps and Sale back pleaded guilty to common assault and resisting arrest, following the transgression outside a nightclub during a pre-season tour in Jersey.
The RPA says it is "surprised" to learn the RFU has charged Cipriani with "conduct prejudicial to the interests of the game", as they consider it an internal club matter.
Cipriani, who moved to Kingsholm in the summer, was fined £2,000 after pleading guilty to the charges and has also been fined the same amount by his club and ordered to do 10 hours community service.
"Given that it related to an off-field, non-rugby related incident that occurred on club time, and had already been dealt with by the Jersey courts, we believe it was appropriate for the matter to be dealt with by the club through its own disciplinary procedures," an RPA statement said.
"As Gloucester have now completed this process, we believe this should close the matter."
Cipriani helped set up a try for Jonny May as England defeated South Africa in the third Test in the summer
A Gloucester Rugby statement on Monday described Cipriani's transgression as a "minor incident".
It added: "While Danny is very apologetic for his actions, we do not believe he is guilty of bringing the game into disrepute and he will continue to get our full support."
Gloucester chief executive Stephen Vaughan previously criticised the timing of the RFU charge, which came before the club had finished their investigation.
Police were called when Cipriani tried to grab a body camera from a doorman at Drift nightclub in The Royal Yacht Hotel, St Helier.
As well as being fined by the court and his club, he was ordered by magistrates to pay £250 compensation to a female police officer.
Three other charges - assault on police, larceny and being disorderly on licensed premises - were dropped.
His club fine will be donated to a local charity for sick and disabled children as well as the players' union charity, which supports players forced to retire through illness or injury.
As part of his community service, Cipriani will work with Gloucester staff to coach local children.
Gloucester begin their Premiership season against Northampton at Kingsholm on 1 September (14:00 BST).