What action declared Martin Luther an outlaw and heretic?

The action that declared Martin Luther an outlaw and heretic was the Edict of Worms. This decree was issued in 1521 by Holy Roman Emperor Charles V during the Diet of Worms, a formal deliberative assembly. In this edict, Luther was excommunicated from the Catholic Church, and his writings were condemned. The document also prohibited anyone from offering him food or shelter, essentially placing him outside the protection of the law. This decision was pivotal because it underscored the growing rift between the Catholic Church and reformers like Luther, further accelerating the Protestant Reformation.

The Ninety-Five Theses laid the groundwork for Luther's critiques of the Church but did not constitute a formal declaration of heresy. The Augsburg Confession was a detailed statement of Lutheran beliefs presented later as part of ongoing discussions with the Catholic Church. The Council of Trent was a response to the Reformation, aimed at reforming the Catholic Church but occurred after the Edict of Worms, thus not directly declaring Luther an outlaw.