Armored Guardian — ruling 1

You can activate the ability that grants shroud in response to this card being targeted by a spell or ability. If you do so, then (if this is the spell or abilities only target) the spell or ability won't resolve since this card will now be an illegal target.

Armored Guardian : règles, fonctionnement et interactions (MTG)

Armored Guardian is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

: Target creature you control gains protection from the color of your choice until end of turn. : This creature gains shroud until end of turn. (It can't be the target of spells or abilities.)

How it works : Armored Guardian

Original English text — Wizards of the Coast / Scryfall

#1October 4, 2004· Wizards of the Coast
You can activate the ability that grants shroud in response to this card being targeted by a spell or ability. If you do so, then (if this is the spell or abilities only target) the spell or ability won't resolve since this card will now be an illegal target.
No other card is named in this ruling.