Does High Ground let creatures that are not able to block, like Skrelv, Defector Mite, block?

Question

I am thinking of including High Ground in my mono-white deck. The deck has a lot of creatures and tokens that cannot block, like Skrelv, Defector Mite and the tokens created by White Sun's Twilight.

Because of the way these cards are worded:

Skrelv, Defector Mite:

Skrelv, Defector Mite cannot block

White Sun's Twilight:

Create X 1/1 colorless Phyrexian Mite artifact creature tokens with toxic 1 and "This creature can't block."

I would assume that this means that High Ground will allow the creatures to block a second creature, but since Skrelv and the tokens cannot block, they still could not block any creatures. Is this correct?

Second, are there any white or colorless cards that can grant the ability to block to cards like Skrelv and these tokens?

Answer 1

I would assume that this means that High Ground will allow the creatures to block a second creature, but since Skrelv and the tokens cannot block, they still could not block any creatures. Is this correct?

Yes:

509.1b The defending player checks each creature they control to see whether it’s affected by any restrictions (effects that say a creature can’t block, or that it can’t block unless some condition is met). If any restrictions are being disobeyed, the declaration of blockers is illegal.

Skrelv says "Skrelv, Defector Mite cannot block", not "Skrelv, Defector Mite can block only 0 creatures." so it's definitely a restriction.

Second, are there any White or Colorless cards that can grant the ability to block to cards like Skrelv and these tokens?

Humility - the property that creatures can't block is an ability (cf. rule 113.2a), but that card has some serious side effects ...

Answer 2

Not white, but Aetherplasm's ability allows you to have a creature blocking that would otherwise be illegal.

Whenever Aetherplasm blocks a creature, you may return Aetherplasm to its owner’s hand. If you do, you may put a creature card from your hand onto the battlefield blocking that creature.

Unfortunately, I don't think a similar effect exists in white.

Answer 3

No, creatures that cannot block still cannot block with High Ground.

509.1b The defending player checks each creature they control to see whether it’s affected by any restrictions (effects that say a creature can’t block, or that it can’t block unless some condition is met). If any restrictions are being disobeyed, the declaration of blockers is illegal.

This is unrelated to the question of how many creatures a creature can block. If instead of "can't block", Skrelv, Defector Mite said something like "Skrelv, Defector Mite can block one fewer creature", then such a thing would theoretically work, but that's not an ability that exists on any cards, and relies on the standard English reading of the ability rather than any particular rule.