Does Lack of Armor Proficiency Prevent Magic Item Use?

[Gale]

A creature wearing armor that they aren't proficient in can't cast spells. Does this also mean they aren't allowed to cast spells through the use of a magic item such as the Ring of Spell Storing or Wand of Magic Missiles?

[JackPhoenix]

Generally, yes. You're still casting the spell from the item, though there are some exceptions.

[col_impact]

Great way to keep a wizard at bay is to force dress the wizard into airtight armor that has been cracked open and then use the mending cantrip to fix/fuse the cracks shut. Voila! No spells for you!