The player said as both are to be worn in the same slot they could not be at the same time, the GM intervened saying that slots are no longer in effect unless the item description made mention of it;
The DM is correct in this case -- magic item 'slots' are a rule from previous editions of D&D (specifically Third and Fourth) and are not used in 5e. (See "Can I Use Older Edition Rules?" from the DDAL FAQ, p.3)
the GM went on it was the case with Belt of Fire Giant Strength & Belt of Dwarvenkind and therefore could not be attuned at the same time.
The DM is incorrect on this point -- there is nothing in the description of either the Belt of Dwarvenkind or the Belt of Giant Strength that says a character cannot attune to other items (or other belt items) at the same time that character is attuned to one of these belts.
I then brought up that somewhere in the DMG there was a mention that 2 items of the same slot could be worn at the same time and that 2 cloaks was mentioned.
You are almost certainly remembering the section of the DMG quoted by Caliban above. Even so, the DMG specifically says that allowing the use of two items of the same kind is an exception -- a DM can allow this, but does not have to, and the advice in the DMG suggests to only allow it when it satisfies 'common sense'.
Please let me know if AL would always forbid to have Belt of Fire Giant Strength & Belt of Dwarvenkind attuned at the same time.
A player can be attuned to both a Belt of Dwarvenkind and a Belt of Giant Strength at the same time, no AL rule prevents it, and the general rule on item attunement only would apply if one of the belts would be the fourth item a character is trying to attune to. But note that you are making an assumption here -- that mere attunement to the item allows you to gain the benefits of the item. For both belts, the key statement is "While wearing this belt,..." So in addition to being attuned, you must also be able to wear both belts to get the benefits from both belts.*
* - It could be argued that the 50% chance of beard-growing from the Belt of Dwarvenkind is an exception -- for that belt, the effect occurs "while attuned to the belt" and does not specify that the belt must be worn (though the use of the phrase "in addition", meaning 'in addition to the effect gained while wearing the belt', might lead some DMs to rule that this effect, also, only applies to those wearing and attuned to the belt.
It is certainly possible to be attuned to an item without using it -- the rules for item attunement state that a character becomes attuned to the item after spending a short rest interacting with it**, and only stops becoming attuned in one of these specific circumstances:
- Another creature attunes to the item.
- Attuned creature no longer meets prerequisites.
- Attuned creature dies.**
- Attuned item spends at least 24 hours more than 100 feet away from attuned creature.
- Attuned creature spends a short rest to 'unattune' from the item.
** - This means that a character who dies during an adventure and is brought back via spellcasting is no longer attuned to his magic items that require attunement until he spends a short rest re-attuning to *each* item: "Attuning to an item requires a creature to spend a short rest focused on
only that item while being in physical contact with it (this can't be the same short rest used to learn the item's properties)." DM's Basic Rules, p.58, emphasis mine. Once the adventure is over, the character can spend as many short rests as he chooses to re-attune to his items.
The presumption appears to be that only one of each 'type' of item can be worn at the same time, but that the rules allow the DM to make an exception when an item 'type' could reasonably allow more than one item to be equipped (for example, and I'm surprised the DMG/DM's Basic Rules don't mention this, magic rings, especially considering that not all magic rings -- *cough*Ring of Three Wishes*cough* -- require attunement).
Since the DMG/DM's Basic Rules leave it up to the DM, without an explicit ruling from the AL otherwise, it's up to an individual DM to allow or disallow this practice. I'm not aware of any such explicit ruling from the AL admins on this point, so I'd check with your DM before claiming such an item, or if it's too late to do that, try to arrange a trade.
--
Pauper
