One to many mapping with different column names fluent nhibernate

[cxg cxg]

I am working with a legacy database, where I have two tables (Staff, Rights) and a joint table (StaffRights). I want to map the one to many relationship/join Staff and staffrights. I have used half day trying to figure this out

With the current code, I get the following exception:

    

    Exception thrown: 'FluentNHibernate.Cfg.FluentConfigurationException' in 

    FluentNHibernate.dll

    Additional information: An invalid or incomplete configuration was used 

    while creating a SessionFactory. Check PotentialReasons collection, and 

    InnerException for more detail.

    Inner exception:System.ArgumentException: The column 'StaffID' has already been added in this SQL builder Parameter name: columnName at NHibernate.SqlCommand.SqlInsertBuilder.AddColumnWithValueOrType(String 

    columnName, Object valueOrType) at NHibernate.SqlCommand.SqlInsertBuilder.AddColumns(String[] 

    columnNames, Boolean[] insertable, IType propertyType)

       at NHibernate.Persister.Entity.AbstractEntityPersister.GenerateInsertString(Boolean identityInsert, Boolean[] includeProperty, Int32 j)}

    Table1 --> Staff

    StaffID: PK

    Name

    Table2 --> StaffRights

    SRID: PK

    StaffID:FK

    RightID:FK

    CreatedTS

    Table3 -->Rights

    RightID: PK

    RightName

    public class Staff

    {

        public virtual int Id { get; protected set; }

        public virtual string Name { get; set; }

        public virtual IList<StaffRights> RightsAssociation { get; set; }

        public Staff()

        {

            RightsAssociation = new List<StaffRights>();

        }

    }

    public class StaffRights

    {

        public virtual int Id { get; protected set; }

        public virtual int StaffID { get; set; }

        public virtual int RightID { get; set; }

        public virtual Staff Staff { get; set; }

    }

    public class StaffMap : ClassMap<Staff>

    {

        public StaffMap()

        {

            Id(x => x.Id).Column("StaffID").GeneratedBy.Native();

            Map(x => x.Name);

            HasMany(x => x.RightsAssociation).KeyColumn("StaffID");

            Table("Staff");

        }

    }

    public class StaffRightsMap: ClassMap<StaffRights>

    {

        public StaffRightsMap()

        {

            Id(x => x.Id).Column("SRID").GeneratedBy.Native();

            Map(x => x.StaffID);

            Map(x => x.RightID);

            References(x => x.Staff).Column("StaffID");

            Table("StaffRights");

        }

    }

    _sessionFactory = Fluently.Configure()

                     .Database(MsSqlConfiguration.MsSql2008.ConnectionString(connStr))

    .Mappings(m =>

    {

        m.FluentMappings.AddFromAssemblyOf<Staff>();

        m.FluentMappings.AddFromAssemblyOf<StaffRights>();

    })

    .BuildSessionFactory();

I have removed the 

    References(x => x.Staff).Column("StaffID");

And I am able to get some results from:

    var staff = session.Get<Staff>(2);

    var rights = staff.RightsAssociation;

    var f = rights.First();

However, as I understand, the mapping shall be bidirectional. What have I misunderstood?