Players agree on "who would win" during tournament

[xyz - Odrael - xyz]

Hello everyone i dont know if i am in the right section but i have to ask some advice.

Premises:
- I was the judge in the last tournament we did 1 week ago
- 2 players were brothers
- in the last round of the tournament they have to face each other, but they noticed that one of them would win the tournament if the other one let him win that match
- so they decided to agree on a win for one of them
- i say that its considered unsportive conduct and they have to play that match much honestly as possible.
- Obviously they played "honestly" and let one of them win the tournament.

After some people arguing that is unfair, i clarifyng that the 1 brothers that win the tournament also beat all other players and he won 5 of 5 match, and the other brother also win 3 of 5 match they take 1st and 3rd place so nothing has really changed.
But it was a lucky situation this time.

The point for me is: how can a judge come over this situation? if 2 players agree on a win for one of them and this would change the tournament ranking what a judge can do?

[Renji Asuka]

They are to be disqualified as it is considered cheating if I recall.

[Jon-Stark]

If its your tournament then you call the shots. Make up your own mind.

[Kitty Trouble]

If its your tournament then you call the shots. Make up your own mind.

If it's sanctioned, no. You have to follow Konami policies. It's allowed to concede for any reason, given that

1) You can't ask your opponent to concede.
2) You aren't offering compensation for your opponent to concede.

[xyz - Odrael - xyz]

Thank you for the replies, so as a Judge the only things i can do:
- Disqualify both if they want to make an agreement
- Prohibit to surrender and force them to play the game

But i think that is easily to come over, exactly as how was happened: nothing can really prevent one of them from playing the Match and throught little mistakes purposely losing to give advantage to the other one.
i dont think i can stay there and make sure that they play the game honestly in all its moves, cause obviusly i got other matches and other calls to pay attention.

[Jon-Stark]

again if its YOUR tournament, YOU can do whatever YOU want.

[xyz - Odrael - xyz]

again if its YOUR tournament, YOU can do whatever YOU want.

This is clear, but im supposing what to do if its not "our" tournament. In realistic terms there's nothing that can really prevent players from agree on the results, it wont matter in big events but in little ones with 10-20 people can change something, thats a problem.

[Kitty Trouble]

again if its YOUR tournament, YOU can do whatever YOU want.

This is clear, but im supposing what to do if its not "our" tournament. In realistic terms there's nothing that can really prevent players from agree on the results, it wont matter in big events but in little ones with 10-20 people can change something, thats a problem.

You can concede at any point for any reason. You can't ask your opponent to concede.

[Jon-Stark]

again if its YOUR tournament, YOU can do whatever YOU want.

This is clear, but im supposing what to do if its not "our" tournament. In realistic terms there's nothing that can really prevent players from agree on the results, it wont matter in big events but in little ones with 10-20 people can change something, thats a problem.

Now youre being confusing, this sounds like YOU are saying it is NOT your tournament. If it is NOT your tournament, then refer to THAT tournaments organizer and just abide by THEIR official rules. If youre playing somewhere that has NO official rules on the matter, then who the hell cares?