NRL CEO Todd Greenberg says Sharks premiership winner Andrew Fifita and Eels winger Semi Radradra weren't considered for Kangaroos selection because of their off-field issues.
Speaking at the Australian Four Nations squad announcement at Rugby League Central on Tuesday, Greenberg said he informed national selectors of the decision last week and that everyone agreed with the ruling.
"Andrew clearly is a talented footballer and played a key role in the Sharks' grand final victory," Greenberg said.
"However, we believe that to wear the Australian jersey, the most prestigious jersey in our game, you should have to distinguish yourself both on and off the field.
"As you know, Andrew is currently being investigated by the integrity unit after wearing an armband supporting someone convicted of a violent offence. While that may not have been illegal, it was in poor taste in the extreme.
"Andrew was suspended for six weeks last year for abusing a junior match official, and has been involved in other off-field incidents.
"We therefore determined that Andrew should not be considered for selection in the Australian squad for the Four Nations tour, and we delivered that advice to the Australian selectors.
"I hope this decision will be seen for what it is – our determination to build a culture in the Kangaroos which every Australian can be proud of – and more broadly, I hope players realise misbehaviour can in future lead to their missing out on their dream of playing for their country.
"I also hope that Andrew will learn from this decision, deal with his off-field issues and return to the Australian team soon."
The situation is slightly different for Parramatta Eels winger Semi Radradra, who is facing charges over domestic violence allegations.
While he has been afforded the presumption of innocence, the NRL didn't want Radradra or the rest of the team to be distracted by the ongoing investigations.
"In regards to Semi Radradra, you will all be aware he is facing serious charges which are due to be heard at the end of the Four Nations tournament," Greenberg continued.
"While the NRL will always give its players the presumption of innocence, we don't want either him or the team to be distracted by this case, and we think that Semi should devote all his time and energy to this very important legal matter.
"Consequently, the NRL has determined that Semi should not be considered for selection for the Four Nations squad, and the selectors have accepted that recommendation."
Greenberg said Tuesday's announcement was a strong reminder that the game will not tolerate off-field indiscretions.
"These are significant decisions, and it is an important day for the game," he said.
"It's a day that we took a stand against poor behaviour off the field, with the ultimate sanction in our sport missing the chance to represent your own country.
"I hope every player in the NRL heeds the warnings and we never have to use this again. But if we have to, we will."
Kangaroos coach Mal Meninga said he supported the strong stance because those wearing the green and gold are the game's "greatest ambassadors".
"I believe all the players should be great role models, not only on the field but off the field," Meninga said.
"I sat with the players before the Anzac Test recently in Newcastle, and they were all of the same view.
"We've drawn a line in the sand around behaviour and I think the Kangaroos should be held in that high esteem that players should be our greatest ambassadors."