Can you ask to use an opponent's dice during a tournament? And do they have to give you their dice? And can you ask to use any dice they have with them?

According to the tournament rules yes on all counts.

I even believe there is a rule that states if your opponent refuses to let you use his or her dice that he or she then forfeits the match.

E.

E-roc can you provide a link?

He can't because there are no such rules. Your opponent does not have to give you his dice. If suspect them of using loaded dice, I suggest confronting them on the matter directly.

Actually, they do have to let you use their dice. I asked someone to use her dice once because she rolled 5 critical hits in a row. She said no, but my judge overheard and said she had to give them to me; I subsequently passed on my bad luck to them. For a while afterwards all the kids would use their opponent's dice if the opponent did well or they were doing crappy.

Everyone asks to use my dice, because they are awesome.

And before you ask, no, I don't have any left.

Can someone provide a link to the official rule or document?

back in the days of Regional tournaments WizKids approved a great deal of judge's discretion on dice. They could, if they felt it was needful, require you to allow your opponent to use the dice you were using (refusing was good for a DQ from the event.) I don't recall that ever getting into the tournament rules, but I think the rules do still allow for the judge or venue to determine some policy and this would still fall under that umbrella.

This is actually a misconception, there never has been a rule that says this.

To have an orange weigh in...

There is NO player's privilege rule. There never has been.

You can ask, but the opponent need not abide.

There is, however, a rule that allows the judge/venue to require it at their discretion.

i have to say, if my dice are rolling hot, there's no way i'm letting my opponent ruin my mojo by smearing their dirty bad luck vibes all over them

That's covered as generally as anything like maps.

As far as rules go I do not believe anywhere it says your opponent has to let you use their dice, but I have heard my judge at my venue say that you can ask you opponent to switch dice if they are not using dice that were manufactured by Wizkids/Neca. Also if you suspect someone of cheating and want use their dice I am sure that a judge could overrule this so you could use their dice, but its not a known rule as far as I know.

I wish I had a copy of these rules as proof, but this rule is just something I have heard my judge says so I hope this helps.

There is nothing specifically addressing this.

The rules give the judge absolute authority, though. Dice etiquette would fall under this umbrella. If the judge wants to say it is fine, that's completely within his rights to do so. If the judge says no, that's also fine.