Norn Sheers in player hands

So the norn's entry says that their shears (+5 mithral keen speed scimitar) function only for a norn.

One of my player nabbed it (and asked for it as a boon from the fey they defeated when offered).

He's smart. He made a UMD check to appear as a member of another race to be able to use them. Should he be able to use them? (They are high levels by the way)

That's exactly what UMD does, let's you use items you otherwise couldn't.

Of course he'd have to make the check every time he attacks. It helps to have a +24 modifier to UMD

You could interpret the need for checks as once per hour if the player keeps the item drawn in hand.

From Core Rulebook:
You make a Use Magic Device check each time you activate a device such as a wand. If you are using the check to emulate an alignment or some other quality in an ongoing manner, you need to make the relevant Use Magic Device check once per hour.

Emulate a Race: Some magic items work only for members of certain races, or work better for members of those races. You can use such an item as if you were a member of a race of your choice. You can emulate only one race at a time.

Would they be mimicking "Fey" or "Norn".
I mean this is potentially one of the more powerful weapons in the game off a drop.