functions.php

<?php
/** 
* Hide Free Shipping for some states
*/ 
add_filter( 'woocommerce_package_rates', 'hide_all_shipping_when_free_is_available' , 10, 2 );

function hide_all_shipping_when_free_is_available( $rates, $package ) { 
	$excluded_states = array( 'AK', 'HI', 'GU', 'PR' ); 
	
	if( isset( $rates['free_shipping'] ) AND in_array( WC()->customer->get_shipping_state(), $excluded_states ) ) {
		unset( $rates['free_shipping'] ); 
	}
	
	return $rates; 
}