Whom vs Who: object Judas + whom [duplicate]

The test itself lies in attempting to apply this new update to a card belonging to Judas, whom is a legitimate user of the system.

Is Judas considered the subject or the object? I'm considering Judas to be the object and hence applying whom after the comma. Is this correct?

I read about whom vs who at LINK, but I'm not sure if I'm applying it correctly to this case. I've also tried the whom+him test by asking Whom does the card belong to? with the answer It belongs to him.

Solution 1:

The name Judas is indeed the object of the phrase in which it appears. However, this has no bearing on the selection of pronoun in a subsequent phrase, where the name can be used in a different function.

If you apply the "whom/him" test to the phrase where you're actually trying to use who/whom, you'll get

Who is a legitimate user of the system? He is a legitimate user of the system.

as opposed to the clearly incorrect version:

Whom is a legitimate user of the system? Him is a legitimate user of the system.