Why is it canonical?

Fuenteovejuna was one of many works created by Lope Félix de Vega y Carpio, one of the leading playwrights and poets of the Spanish Golden Age (The Siglo de Oro) when Spanish artists and writers flourished thanks to the support of a Spanish monarchy that had become a world power only relatively recently. It was released as a part of a collection of Lope de Vega's works, but one of his most enduring and influential.