Zack Snyder hinted one of his next movies will be a "faithful" adaptation of King Arthur, but that's not possible to do considering the many stories out there. The project is still in its earliest stages, and there have been no official announcements concerning it, only Snyder's word. However, there is already one massive problem with the idea of a "faithful" version of King Arthur: it is impossible to be faithful to the complex and varied Arthurian legends.
In an interview with Minutemen to promote his upcoming version of Justice League, Snyder said that he had "been thinking about some kind of retelling, like real sort of faithful retelling of that Arthurian mythological concept. We'll see. Maybe that will come at some point." He did not elaborate further on what the movie could entail or when it would be released.
While there is not much information about Zack Snyder's potential King Arthur film beyond this quick statement, the idea of a "faithful" retelling of King Arthur has already drawn a fair share of criticism. It is impossible to create a faithful retelling of King Arthur because there is no one true Arthurian legend. Instead, there exist centuries' worth of tales, with different iterations existing for each story. Snyder may have meant that he'd be faithful to the historical figure of King Arthur, but even then there is debate as to whether King Arthur really existed.
To understand why it's impossible to be truly faithful to King Arthur, it's useful to think of the mythology surrounding him as a patchwork that's been added to over time. The legend of King Arthur was popularized by Geoffrey of Monmouth's 12th-century work the History of the Kings of Britain, but various iterations of Arthur appear in even earlier Welsh and Breton myths. King Arthur's legend continued to evolve from Monmouth's work, as other writers, including French writer Chrétien de Troyes, created their own versions of King Arthur's story. De Troyes added some of the more well-known Arthurian staples to the legend, including Lancelot, but his version, like Monmouth's, is by no means definitive. Many more writers expanded on King Arthur's tales, so the legend existed in a state of constant growth that would be impossible to adapt faithfully.
Perhaps Snyder was talking about faithfulness to King Arthur in a historical context. However, that, too, is not possible, since historians continue to debate whether King Arthur even existed. Even if he did, his story would certainly not look like the Arthurian tales known today. King Arthur as a historical figure is featured in the 9th-century Historia Brittonum, which lists battles he fought against the Saxons during the 5th and 6th centuries. However, the accuracy of this text and others mentioning King Arthur has been questioned. Even if Arthur existed, these historical accounts - and the Arthurian legends - were written centuries after he was dated to have lived, meaning that they could not be truly faithful either.
Suggesting that a "faithful" adaptation of King Arthur exists eliminates the fascinating complications that come with a mythology as vast as King Arthur's. Snyder has the chance to put his own spin on Arthurian legend - he could even adapt one of the lesser-known Arthurian stories, many of which are more entertaining and bizarre than those audiences may already be familiar with - but first he needs to realize the impossibility of the task he has set himself and move on from the false concept of a "faithful" retelling of King Arthur.