do_action Parameter with wp_deregister_style

I want to remove a stylesheet via do_action function with a parameter I make this:

add_action( ‘wp_print_styles’, ‘deregister_css’, 100,1 );
function deregister_css($a){
wp_deregister_style( $a );
}

do_action(‘wp_print_styles’, ‘layerslider’);
Why does this not work??
How do I get this to work??

Best regards gongl