回複：Does Costco's personnel have the right to open my bag?

如果您仔細閱讀您的membership agreement
(http://www.costco.com/Images/Content/Misc/PDF/WelcomeBrochure04.pdf)
In Page 11 General Policies items 4
"Costco reserves the right to inspect any customer, backpack, briefcase etc,. upon entering or leaving the warehouse."
所以您在申請Costco membership card的時候已經同意讓對方搜索您的bag。

(下一次，簽屬任何membership申請時，請仔細閱讀每一條規定)