Per Costco’s Membership Privileges and Conditions, Costco can revoke memberships for any reason they deem fit, but they mostly do so when people exploit their return policy.
Costco doesn't limit returns to a specific time frame on most items and allows for long periods to return certain products like electronics, which have a 90-day frame for return.
The system’s still abused by some, like one woman who returned a used Christmas tree in January after it was dead and a couple who asked for a refund for a used chicken coop.
Cancellations of memberships depend on what’s being returned and why, and if you're excessively returning multiple items on every trip to Costco, you will end up looking dubious.
Costco lets its managers decide whether they should revoke memberships. To avoid getting flagged, use common sense and determine if the item rightfully deserves to be returned.
However, you won’t get in trouble for returning slightly used items if there's a valid reason behind the choice. On a brighter note, you’ll be refunded for your revoked membership.