Melbourne NRL star Cameron Munster is voluntarily entering a treatment facility for the next four weeks to deal with his alcohol use, with the Storm warning he's on his last chance with the club.

An emotional Munster addressed the media on Tuesday along with Storm teammates Brandon Smith and Chris Lewis, after all three were sanctioned by the NRL for their post-season antics.

Issued with breach notices alleging they brought the game into disrepute, the trio will miss the 2022 season opener and face various fines, with Munster hardest hit with a $30,000 penalty.

Warriors youngster Reece Walsh was issued with a similar breach notice after his Gold Coast arrest, which has led to a drug investigation.

The 19-year-old Walsh faces a two-game ban and a $5,000 fine.

Two undated videos surfaced online after the Storm's NRL finals exit.

The initial vision appeared to show Munster, Smith and several other people in a room with a white substance on a table, while a second video showed Munster dancing on the same table.

Storm boss Justin Rodski said his players hadn't admitted taking any drugs and the NRL was unable to test them given its testing policy, which covers illicit drugs, doesn't extend into players' off-season.

"Through excessive consumption of alcohol and intoxication the players have limited memory of what did or didn't take place in that hotel room," Rodski said.

He defended the one-game bans and said the "totality of sanctions and penalties handed down across the NRL and the club were significant and serious".

Munster said he had had a "difficult relationship" with alcohol and that he needed to take further steps to change his behaviour.

"I thought I'd dealt with this issue but clearly I still have some hurdles to overcome," he said.

"I made the decision in consultation with the club doctor to seek some help with this battle.

"Starting tomorrow, I'll be attending a treatment facility for the next four weeks.

"I know I've let a lot of people down … hopefully you'll see by my actions that I'm dedicated to change."

Melbourne have put the representative playmaker on a 12-month booze ban, fined him $100,000 fully suspended, and axed him from the leadership group.

Rodski said if Munster breached the alcohol ban he would cop the hefty fine and face the Storm's board, which would decide his fate.

Asked if the 27-year-old was on his last chance after previous disciplinary issues, Rodski replied: "I think you could take from this that he is, yes."

NRL boss Andrew Abdo said the players, who would also undergo education and training, had let the rugby league community down.

"There is no excuse for the behaviour we have seen over the past week," Abdo said in a statement.

"These sanctions are designed to include an element of rehabilitation and development as well as having consequences for the individual and team."