I've been having a debate with a player, and as much as I'd like be as fair as possible I also don't like players trying to bend the rules.  With that being said the spell reads as follows:

"Magical darkness spreads from a point you choose within range to fill a 15-foot-radius sphere for the duration. The darkness spreads around corners. A creature with darkvision can't see through this darkness, and nonmagical light can't illuminate it.

If the point you choose is on an object you are holding or one that isn't being worn or carried, the darkness emanates from the object and moves with it. Completely covering the source of the darkness with an opaque object, such as a bowl or a helm, blocks the darkness.

If any of this spell's area overlaps with an area of light created by a spell of 2nd level or lower, the spell that created the light is dispelled."

I have argued that you are not allowed to cast it on an individual, the player came back and said they were casting it on an arrow in the quiver of the enemy.  I came back citing the RAW "object you are holding or one that isn't being worn or carried".  The player states that the arrow is being carried by the quiver and not by the enemy.  I feel this is him just grasping at straws but he swears he's seen it done and used in Adventure League.

As the DM I have ruled against this being allowed to be cast on an enemies objects no matter what they are being carried in, but I would like to know how you others DM's would have ruled.

Thanks - Chig232

I second that the arrow is clearly being carried by the person who is holding/wearing/carrying the quiver the arrow is located in.  A hardline interpretation of the spell would say that you could cast it on an arrow in your quiver that you are carrying/holding/wearing, but not on the arrow in anyone else's quiver, unless they weren't holding/carrying/wearing it at the time.

Now, if you cast it on an arrow laying on the ground, and someone picked it up and put it in their quiver, the spell would not end.  The targeting rule only applies at casting, not during the duration.

if you as DM say the arrow is  carried, then it is. 

Take all the money from his wallet. It's not his money, it's the wallet's money, so he won't object

;)

Or more seriously, point out that anything not carried or worn by a creature that is subjected to a fireball will catch fire.

That would mean that anything they have in backpacks, quivers, pouches, etc. would be susceptible to that, too.

Or that anything that reduces your carrying capacity, is in fact carried by you.

Quote from Chig232 >>

The player states that the arrow is being carried by the quiver and not by the enemy.  I feel this is him just grasping at straws but he swears he's seen it done and used in Adventure League.

 You are absolutely correct and the player was being ridiculous. Compare darkness to light which does allow you to target objects in an unwilling creature's possession. At the very least, it should require a failed saving throw to accomplish.

And mjolnir can be easily lifted by tying a string to the handle. "I don't have to be worthy because I'm not lifting it, the string is..."

If it's weight is supported and being moved by someone, it is carried by them.

Just to note: Adventure League isn't a scheme of DMs being monitored by cameras or omniscient WotC people ready to flog at any break in RAW. Adventurer's League is aimed at being a "closer" to RAW game and to "minimise", not abandon, homebrew. Some homebrew is actually permitted by Adventurer's League with some DMs offering rewards and bonuses that are homebrew but "officially permitted". AL DMs do still have some leeway in how the adjudicate rules. AL is a "less, not none" style in terms of ad hoc rules/homebrew. So even if the player did see this be done in an AL game it doesn't matter - because it doesn't necessarily mean it was RAW.

It also doesn't matter because that wasn't your game and every game will be different, especially with a different DM. 

But yes, in agreement with everyone else : the player is just trying to cheat the system by trying to bend phrasing and doing a shit job of it. So, no, RAW, you cannot cast Darkness on an enemy's arrow if on their person in any way, quiver or not.