Sell only to CA - Single Shipping Class

functions.php

<?php

/**
 * Looking to make a shipping class only eligable for a specific state
 */
 
add_filter( 'woocommerce_states', 'wc_sell_only_states' );
function wc_sell_only_states( $discountstates ) {

	$discountstates['US'] = array(
		'CA' => __( 'California', 'woocommerce' ),
	);

	return $discountstates;
	
}