Can black luster soldier - envoy of the beginning be special summon from the graveyard?

Initially, a monster who can only be special summoned, may only reach the field by following the method on its card - unless an effect specifically states otherwise.

As for reviving them from the graveyard, there are two subsets of special summon-only monsters. They are;

"Can only be Special Summoned by..."

If this kind of monster is properly special summoned by the listed method, you can bring it back with cards like Monster Reborn. The two Envoys belong to this group, as do all Rituals, Fusions and Synchros by default, except for a few who have text that include them in the second group below.

"Cannot be Special Summoned except by..."

Even if this monster is properly special summoned by the listed method, it can't be brought back by cards like Monster Reborn. Dark Armed Dragon and Judgment Dragon are examples of this kind, as do a few Rituals, Fusions or Synchros, like Dark Paladin, who cannot be special summoned except by Fusion Summon.

Lastly, again unless specificaly stated otherwise, the card's special summon requirements are from the hand only. You cannot remove a Light and Dark monster to special summon the Envoys from the graveyard, they can only be special summoned this way while in hand. However on the plus side, if they were properly special summoned, you can bring them back with Monster Reborn, and they do not need another Light and Dark monster to be removed when you do this.