Weasel does not mean you are banned. If you log into the game and are met with a "Not so fast..." message, that means you are banned. Weasel errors are, more generally, a networking error resulting in a disconnection from the game. More information can be found on the corresponding page for the error code: https://help.bungie.net/hc/en-us/articles/360048717852-Error-Code-WEASEL