Widnes Vikings have been fined £20,000 by the Rugby Football League after fans ran onto the pitch following August's Challenge Cup semi-final defeat by Castleford Tigers.
The Vikings lost the match 28-6 at Leigh Sports Village on 10 August.
Police and stewards had to intervene to restrain spectators from the Widnes section.
The club has been instructed to pay £10,000 immediately, with an additional £10,000 suspended for 12 months.
Widnes, who the RFL acknowledged for their full cooperation with the investigation, must also pay £4,000 costs.
The RFL said in a statement: "Rule D1.10b states that clubs are 'responsible to the RFL for the actions of their spectators and all persons purporting to be their supporters, and are required to use their best endeavours to take all precautions to ensure that their spectators and all persons purporting to be their supporters do not threaten, abuse or assault third parties'.
"Clubs must also ensure that 'their spectators, or people purporting to be their supporters, do not damage property, or invade the pitch, or pitch surrounds, or throw missiles on the pitch, or act in a disorderly or improper manner before, during or after the conclusion of matches'."
Widnes chief executive James Rule said in a joint statement with the RFL that the club apologised for the disorder.
"We will continue to work with the police, the RFL and Halton Borough Council to implement banning orders to all involved," he said.
"Whilst we accept the tribunal's ruling and recognise our responsibilities as to the behaviour of our fans, it is important for us to recognise that the acts were not representative of our true supporters and the spirit of Widnes Vikings."