Is it possible to make a Ban Function using Data Store?

Yes it is possible

Here is an example:

--Server Script
local datastore = game:GetService("DataStoreService"):GetDataStore("Bans")

game.Players.PlayerAdded:connect(function(plr)
	local key = "user_" .. plr.UserId

	local banned = Instance.new("BoolValue", plr)
	banned.Value = datastore:GetAsync(key) or false
	banned.Name = "Banned"

	if banned.Value == true then
		plr:Kick("You have been banned!")
	end


	banned.Changed:connect(function()
		datastore:SetAsync(key, banned.Value)

		if banned.Value == true then
			plr:Kick("You have been banned!")
		end
	end)
end)