In the most recent episode of dragon ball super (episode 115) we were shown the new fusion; Kefla.
This fusion was achieved by the use of Potara earrings. But from what I remember items and such weren't allowed. Otherwise universe 7 would bring a lot senzu beans for survival. Potara earrings aren't items that belong to the fighters and are therefor external. Isn't the use of this against the universal tournament rules?
Apparently they are allowed in the tournament. Otherwise Zen-Oh sama would have erased Kefla instantly for cheating.
Also, the DBZ wikia states it openly in the rules of the Tournament of Power:
Fighters cannot be killed, use weapons, or use healing items (e.g. Senzu Beans) during the match.
However items that are not dangerous by themselves such as the bottle Master Roshi uses as part of the Evil Containment Wave were permitted by the Zen-Ohs, though it is implied that was because they thought the technique was cool.
Potara Earrings are permitted as well thus Potara fusion is allowed and the items are not dangerous weapons that can directly harm an opponent.
If someone is killed by their own attack being deflected by someone else or by a inherit flaw in a fighting technique, it's not considered a violation of the rules.
I think the best answer to this would be that anything that Zeno finds amusing or entertaining can be considered safe. Even though Roshi used the bottles and Krillin used the sunglasses and the shoe, Zeno was likely entertained by the same and he didn't have any issue with it. It's obvious he's going to be very amused by the fusion so all though they did break a rule, they aren't going to get disqualified.
I'm also certain of the fact that suppose Zeno were to believe that the fighters eating the Sensu bean would probably make them stronger and fight harder, they honestly wouldn't care as long as it entertains them.
