Dice

[Red5bv06]

I rolled a 20-sided dice. My opponent called a judge and said only 6-sided dice could be used for effects. My opponent said this was announced as official at another Battle Road (but not at this one). The judge suggested that I re-roll.

It is my understanding that the (Head) Judges can allow/dis-allow any dice he/she wants (if he/she decides it to be unfair), so I abided by the decision.

I would have greatly preferred if some announcement allowing only 6-sided dice had been made at the beginning of the tournament, however. So finally the questions:
1. Does the announcement have to be made at the beginning or can a (fair) dice be dis-allowed at any time (even in the middle of a match (which hurt the most))?
2. Is there an official ruling that I am not aware of that says only 6-sided dice can be used (regardless of the judge)?

That is all. I doubt it would have made a difference in my game, but something to know for the future none-the-less.

[PokePop]

There is no official ruling about only 6-sided dice being allowed.
You are correct that the Head Judge has complete control over what dice are allowed or not allowed.

It would be a good idea if they have a "6-sided only" policy to announce it at the beginning.

Hopefully the judge was not just responding to what was claimed to "official" based on what the other player said.
You say he "suggested" you reroll rather than saying he "directed" or "told" you to reroll.
Not sure if you meant it that way or not.

Also, bear in mind, you always have the right to appeal to the Head Judge and/or state your case for your side. At the time it is happening is when that needs to be done.