Does shroud prevent the controller of a permanent from targeting it with their own spells?

Shroud is a static ability defined in CR 702.18a: a permanent or player with shroud cannot be the target of spells or abilities. This protection is absolute — it does not distinguish between who controls the targeting spell or ability. Unlike hexproof, which only protects from opponents' targeting, shroud blocks everyone, including the permanent's own controller.

CR 509.1a requires players to choose legal targets when casting spells. A permanent with shroud is simply not a legal target for any spell or ability, full stop. If you attempt to target your own shroud creature with a spell, that spell is illegal and cannot be cast targeting that creature.

This is the critical difference between shroud and hexproof (CR 702.11a): hexproof only prevents opponents from targeting the permanent, so its controller can still target it freely. Shroud has no such exception.

Concrete example: You control a Gladecover Scout (which has hexproof) and a Slippery Bogle with shroud. You want to attach an Aura by casting it. You can target Gladecover Scout with your own Aura spell, but you cannot target the Slippery Bogle — your own shroud creature is off-limits to your own spells too.

If you want to buff or target your own creature, make sure it has hexproof rather than shroud, or find a way to remove the shroud ability first.