Pala'amo has spent two seasons with Leeds since joining from Leinster
Leeds prop Fosi Pala'amo has had his application for a visa to play in the UK rejected.
The Samoa international joined Leeds in 2007 but has not been able to return to the UK since going home to play in the Pacific Nations Cup in the summer.
He is now unable to reapply for a visa for another 12 months, ruling him out of the rest of the Premiership season.
Head coach Neil Back told BBC Radio Leeds "Fosi's disappointed, he would have been a key player for us."
American international Mike MacDonald is also awaiting a visa, with a decision expected in the coming days.
"We are hopeful of hearing some more positive news on Mike MacDonald regarding his visa," chief executive Gary Hetherington told the club's website.