Binding a CollectionViewSource within a DataTemplate

'ContentTemplate' is a DataTemplate that displays an object which has a member 'FooList' (an ObservableCollection).

<DataTemplate x:Key="ContentTemplate">
    <ListBox ItemsSource="{Binding Path=FOO}">
        ...
    </ListBox>
</DataTemplate>

I need to be able to filter that FooList using a CollectionViewSource. This is usually been straight forward but I can't seem to get the binding to work within a DataTemplate. I attempted to this:

<DataTemplate x:Key="ContentTemplate">
    <DataTemplate.Resources>
        <CollectionViewSource x:Key="CVS" Source="{Binding Path=FooList}" Filter="FooFilter"/>
    <DataTemplate.Resources>
    <ListBox ItemsSource="{Binding Source={StaticResource CVS}}">

The errors I get from this is:

System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=FooList; DataItem=null; target element is 'CollectionViewSource' (HashCode=52991666); target property is 'Source' (type 'Object')

Which sounds to me like it's looking for 'FooList' on the CollectionViewSource instead of the object bound to the DataTemplate.

So... how do I get this to look at the correct object?