<CheckBox Content="C1" Height="16" Name="C1" IsEnabled="{Binding ElementName=C16, Path= IsChecked}"/>

IsEnabled = not IsChecked

xmlns:local="clr-namespace:tst;assembly=tst"

        <local:NotConverter x:Key="notConverter"/>
        <Style x:Key="CheckBoxStyle" TargetType="{x:Type CheckBox}">
            <Setter Property="Height" Value="16"/>
            <Setter Property="IsEnabled" Value="{Binding ElementName=С16, Path=IsChecked, Converter={StaticResource notConverter}}"/>
            <Style.Triggers>
                <Trigger Property="IsEnabled" Value="False">
                    <Setter Property="BorderBrush" Value="Red"/>
                    <Setter Property="IsChecked" Value="False"/>
                    <!--<Setter Property="Background" Value="#FFF5F9FF"/>-->
                </Trigger>
            </Style.Triggers>
        </Style>