The challenge Cup was thrown into disarray yesterday when the tie between Halifax and Batley was called off less than four hours before kick-off because Halifax had fielded an ineligible player in the previous round.
The league is investigating the circumstances behind the 22-year-old prop, Michael Ostick, playing in the fourth-round victory over Swinton, having already played for Rochdale against Lezignan earlier in the competition.
The last time the situation arose was when Hull fielded Jamie Thackray two years ago, despite his having already appeared for Hunslet.
Hull were fined £100,000 – £60,000 of it suspended – but not expelled from the competition. The league says it has tightened up its rules since then and has the option of re-instating Swinton or awarding the fifth round tie to Batley.
The Halifax chairman, Michael Steele, said that the club was co-operating fully with the RFL and was conducting its own internal inquiry.
The reward for whoever emerges from this mess will be a quarter-final at home to the Catalan Dragons.