unregister_setting( string $option_group, string $option_name, callable $deprecated = '' )

function unregister_setting( $option_group, $option_name, $deprecated = '' ) {
	global $new_whitelist_options, $wp_registered_settings;

	if ( 'misc' == $option_group ) {
		_deprecated_argument( __FUNCTION__, 'WP-3.0.0',
			/* translators: %s: misc */
			sprintf( __( 'The "%s" options group has been removed. Use another settings group.' ),
				'misc'
			)
		);
		$option_group = 'general';
	}

	if ( 'privacy' == $option_group ) {
		_deprecated_argument( __FUNCTION__, 'WP-3.5.0',
			/* translators: %s: privacy */
			sprintf( __( 'The "%s" options group has been removed. Use another settings group.' ),
				'privacy'
			)
		);
		$option_group = 'reading';
	}

	$pos = array_search( $option_name, (array) $new_whitelist_options[ $option_group ] );
	if ( $pos !== false ) {
		unset( $new_whitelist_options[ $option_group ][ $pos ] );
	}
	if ( '' !== $deprecated ) {
		_deprecated_argument( __FUNCTION__, 'WP-4.7.0',
			/* translators: 1: $sanitize_callback, 2: register_setting() */
			sprintf( __( '%1$s is deprecated. The callback from %2$s is used instead.' ),
				'<code>$sanitize_callback</code>',
				'<code>register_setting()</code>'
			)
		);
		remove_filter( "sanitize_option_{$option_name}", $deprecated );
	}

	if ( isset( $wp_registered_settings[ $option_name ] ) ) {
		// Remove the sanitize callback if one was set during registration.
		if ( ! empty( $wp_registered_settings[ $option_name ]['sanitize_callback'] ) ) {
			remove_filter( "sanitize_option_{$option_name}", $wp_registered_settings[ $option_name ]['sanitize_callback'] );
		}

		unset( $wp_registered_settings[ $option_name ] );
	}
}