The U.S. Federal Communications Commission (FCC) warned hotels and other businesses on Tuesday that blocking people from using their personal Wi-Fi is unlawful. The announcement came after an investigation revealed that Marriott International blocked their guests' hot spots.

"The Enforcement Bureau has seen a disturbing trend in which hotels and other commercial establishments block wireless consumers from using their own personal Wi-Fi hot spots on the commercial establishment's premises," the agency said in a statement on its website.

Marriott International was fined $600,000 for the "unlawful interference." The hotel company also promised that it won't block its guests from using their personal Wi-Fi. But it filed a petition, along with other hotels, to the FCC to change the policy as they need to protect the reliability of their own networks, according to the Wall Street Journal.

"Marriott remains committed to protecting the security of Wi-Fi access in meeting and conference areas at our hotels. We will continue to look to the FCC to clarify appropriate security measures network operators can take to protect customer data, and will continue to work with the industry and others to find appropriate market solutions that do not involve the blocking of Wi-Fi devices," the company said.

The FCC rejected the petition and decided to release this warning instead. It is also encouraging people to file an official complaint with the agency if they suspect that their Wi-Fi is being blocked by the business so that it can perform necessary investigations.

"Consumers must get what they pay for," said FCC Chairman Tom Wheeler.

"The Communications Act prohibits anyone from willfully or maliciously interfering with authorized radio communications, including Wi-Fi. Marriott's request seeking the FCC's blessing to block guests' use of non-Marriott networks is contrary to this basic principle," he added.