This is a fork of this: https://gist.github.com/ChromeOrange/3200974 which allows you limit individual products in WooCommerce to a quantity of 1 for that item, per order. It also removes the quantity field on any items with this setting turned on. For this fork I simply added the comments to make it a WP plugin instead of needing to be added to…

woocommerce-disable-quantity-per-product.php

<?php
/**
 * Plugin Name: WooCommerce Disable Quantity Per Product
 * Plugin URI: https://gist.github.com/FiddlerStudios/78308937c3550e5d7d26
 * Description: Allows you to disable the quantity option on individual products.
 * Version: 0.2
 * Author: Andrew Benbow
 * Author URI: https://gist.github.com/ChromeOrange
 */
 
add_filter( 'woocommerce_is_sold_individually', 'cj_woocommerce_is_sold_individually', 10, 2 );

function cj_woocommerce_is_sold_individually( $value, $product ) {
	
	$isi = get_post_meta( $product->id, '_custom_sell_individually', TRUE );

	if ( $isi == 'individual' ) :
		$return = true;
	endif;

	return 	$return;
	
}

if ( is_admin() ) :

        add_action( 'woocommerce_product_options_dimensions', 'isi_write_panel');
        add_action( 'woocommerce_process_product_meta', 'isi_write_panel_save' );

        function isi_write_panel() {
            echo '<div class="options_group">';

            woocommerce_wp_select( array( 	'id' 		=> '_custom_sell_individually', 
											'label' 	=> __('Sell Individually?', 'woocommerce'), 
											'options' 	=> apply_filters('woocommerce_product_visibility_options', 
												array(
													'multiple' 		=> __('Multiple purchases allowed', 'woocommerce'),
													'individual' 	=> __('Individual Only', 'woocommerce')
												)), 
											'description' => __('Limit the product to one per order?', 'woocommerce') ) );

            echo '</div>';
        }

        function isi_write_panel_save( $post_id ) {
            $_custom_sell_individually = esc_attr($_POST['_custom_sell_individually']);
            update_post_meta($post_id, '_custom_sell_individually', $_custom_sell_individually);
        }	

endif;
?>