gistfile1.php

<?php

/**
 * Check the cart for specific classes, remove UPS Shipping method if they are present
 * 
 * REMOVE THE TOP <?php if there is no ?> before (or you have an error after adding this)
 * 
 * Add the code to your theme functions.php file
 */
add_filter( 'woocommerce_package_rates', 'unset_usps_shipping_method' , 10, 2 );
function unset_usps_shipping_method( $rates, $package ) {
 
	// Setup an array of shipping classes that do not allow UPS Shipping (@todo change this)
	$shippingclass_array = array( 'no-usps' );
 
	/**
	 * loop through the cart looking for the products in the array above
	 * and unset the Free shipping methods as necessary
	 */ 
	foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {

		$shipping_class = get_the_terms( $values['product_id'], 'product_shipping_class' );
 
		if ( isset( $shipping_class[0]->slug ) && in_array( $shipping_class[0]->slug, $shippingclass_array ) ) {
		
      			/**
			 * Unset the shipping methods here
       			 */
       		foreach( $rates as $key => $rate ) {
       		    if (strpos($key,'usps') !== false) {
       		        unset( $rates[$key] );
       		    }
       		}
       		
		}

	}
 
	// Return what's left of the $rates array
	return $rates;
 
}