The Newcastle Knights have announced the release of Dylan Phythian from the club, following a second contravention under the NRL's Illicit Drugs Policy, which automatically incurs a 12-match suspension.
Phythian, 22, played three games for the Knights since making his NRL debut in 2016 but suffered a season-ending knee injury in round one last year.
Further complications with surgery delayed his start to the 2018 season with the club.
"It's a sad day for Dylan and the club but it's clear this culture doesn't fit with us," Knights CEO Phil Gardner told NRL.com.
"We were left with no option. We have to have a club that we're proud of and that the community is proud of.
"We are a developing club so the behaviour sets a benchmark. As a person you've either got integrity or you don't. We keep our word and we have to expect the same."
The Knights say they will provide Phythian with counselling support with Gardner hopeful the Lakes United junior could return to the game in the future.
"We will support Dylan, we'd like to see him back in the game and he has accepted that," Gardner said.
"The game is great in how it looks after people and offers them a second chance, but you've got to be willing to do that too."
Newcastle have won two of their first three matches of the 2018 season, and face the competition-leading St George Illawarra Dragons in Wollongong on Sunday.