The Rhinos have a partnership with the Hawks in which players not required for Super League duty can be dual-registered to turn out for the Championship club. Leeds wanted Leuluai and fellow front rower Richard Moore to gain match practice with Hunslet against Leigh on Sunday after not figuring in their opening match of the season against Hull last Friday.
However, the Rugby Football League say they have been told by the UK Border Agency that, under the terms of his visa, Leuluai is unable to become a dual-registered player.
The ruling, which only affects overseas players, will have repercussions throughout the game.
It follows the cost-cutting decision to scrap the Super League clubs' Under-20s competition which was used to keep fringe players active and ease others back into action from injury.
Bradford were hoping to allow Australian centre Adrian Purtell to make his comeback from a heart attack with their partnership club Dewsbury but will now be forced to throw him straight back into Super League when he completes his recovery.
A League spokesman said: "The RFL has recently lobbied the UKBA for a change to the rules which prevent players on tier-two visas playing for a second club on a short-term arrangement.
"This follows on from changes to the Super League Academy structure, which from 2013 is an exclusively Under-19s competition, an arrangement that means open-age overseas tier-two visa players returning from injury cannot gain match fitness on short-term loans or dual registrations.
"Dialogue with the UKBA continues but the UKBA have confirmed that, until any change in circumstance is agreed, under existing provisions no player on a tier two visa can be dual registered."
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