Walmart used to allow emotional support dogs and emotional support animals in their stores but now Walmart does not allow emotional support dogs or any emotional support animals into it's stores.
Walmart doesn't have to allow emotional support animals into it's stores nor does any other store since the ADA doesn't recognize emotional support dogs or emotional support animals as service animals if they haven't been specially trained to perform certain tasks.
Some other places may allow emotional support animals into their stores but it's up to the store as to what they allow.