I was placed on Admin. leave because I lost 7 money orders that were rent payments made by tenants. I restored all funds immediately. I was contacted by a tenant and told that my ex boss stated that I was put on Admin Leave for taking money. Also the tenant said that my ex boss told the tenants not to have any contact with me and if they see me calling not to answer. The tenants felt threatened by her demand
There are no laws that place a muzzle on people because they are you former (or current) employer. They can talk about you as much as you can talk about them. The same laws of slander apply to them as anyone else.