Marum, who is also the chairman of selectors, said any player taking part in a lower level competition is not eligible.
“These are the only four competitions we are selecting players out from. There are a lot of players playing overseas but when we start picking players from different competitions, it’s going to be a total mess.
“I’ll give an example of Israel Eliab who went away and played with the London Broncos. He came back struggling.
“We started last year with the players we picked and they provided the result," said Marum.
Marum went on to back the Kumuls side that will take on the Cook Islands in this Saturday’s Pacific Test, saying it’s a team that was picked on form and one which can produce a win.
“I think we have a good team. We have a good chance of winning this game,” said Marum.