Secret Lair x The Walking Dead was probably the most controversial Magic: The Gathering product of 2020 for multiple reasons, and one of them is the fact that the cards featured in this limited ediction collector's box are legal in Commander format, but it looks like their legality may have been changed, according to the Gatherer.
The official MTG database shows that all the five non-token cards from Secret Lair x The Walking Dead x Secret Lair are not legal in any formats. These cards were originally announced to be legal in Commander and other Eternal formats, but if the Gatherer is correct, and not just a result of a glitch, that means that these cards can no longer be played in those formats.
While some fans enjoyed seeing characters from another IP featured in cards that are legal in Commander and other Eternal formats, many expressed their criticisms to Wizards of the Coast's decision to legalize them in these formats. Back in September, fans started a petition to ban the cards in Commander, but the Commander RC ultimately decided to not ban them, and explained why.
Since no official announcement has been made by Wizards of the Coast about this change, this is most likely the result of a glitch in The Gatherer.
Last October, Wizards addressed the widespread community backlash about the crossover Secret Lair product.