Block the specified user(s).
drush user-block
users : A comma delimited list of uids, user names, or email addresses.
Block the users with name, id, or email 5 or user3, uids 2 and 3, names someguy and somegal, and email address of billgates@microsoft.com
drush user-block 5,user3 --uid=2,3 --name=someguy,somegal --mail=billgates@microsoft.com