Amazon has been found to be liable for in-app purchases that children have made without permission from their parents, as decided by a federal judge.

The ruling ends the case filed by the Federal Trade Commission against Amazon back in 2014, as Amazon then refused to comply with the FTC's request to revise its in-app purchase policy. The commission alleged that Amazon unlawfully billed thousands of customers millions upon millions of dollars through in-app purchases made by children without the authorization from their parents.

According to the U.S. District Court for the Western District ​of​ Washington state, Amazon did not implement proper safeguards to keep children from making the unauthorized purchases.

"Given the design of the Appstore and procedures around in-app purchases, it is reasonable to conclude that many customers were never aware that they had made an in-app purchase," said the court in its ruling.

U.S. District Judge John Coughenour acknowledged the over 1,500 customers that were denied for refunds for unauthorized purchases, adding that it is Amazon's policy that all in-app purchases made are nonrefundable and final.

Coughenour, however, did not approve a request by the FTC to subject Amazon to an oversight period of 20 years, as the company has already changed its policies and procedures for in-app purchases since the initial filing of the case.

Previously, in-app purchases on apps from the Amazon Appstore did not need passwords, making it possible for developers to abuse the fact by blurring the lines between paid and free content, especially in games for children. The system has since been updated to provide informed consent for in-app purchases, but that did not come around until July 2014.

The ruling on Amazon's liability did not specify the amount of monetary relief for the affected users, with the figure to be determined over the coming months. The FTC is pushing for full refunds for all unauthorized in-app purchases.

The amount will most likely be a significant one, with past cases against other tech giants serving as examples. Both in 2014, Google refunded $19 million, and Apple paid back $32.5 million to users for in-app purchases made by children without the consent of their parents.