The U.S. Navy has ordered commercial flights to the military base at Guantanamo, Cuba canceled because of a regulation that had been overlooked for years, outraging lawyers who use the flights to visit their clients at the detention facility.

The order comes just days after lawyers of detainees held at Guantanamo sent a letter to U.S. Defense Secretary Chuck Hagel complaining of tougher treatment of detainees by the base commander who arrived last summer. At least 25 suspected terrorists held at the detention facility are participating in a hunger strike, which lawyers say is a result of the treatment they are receiving.

Navy Capt. John Nettleton, commander of the U.S. base at Guantanamo, notified the small airline, IBC Travel, in late February, according to military officials. The airline was directed to stop flying into Guantanamo by April 5, but the Navy said it will give them until May 1 to comply with the order.

A spokesperson for the base, Kelly Wirfel, told CNN the decision was made after a review of flight operations at the base that found that the airline was violating two base regulations. The flights were found not "directly connected with or in support of U.S. government businesses," and not, "in connection with U.S. Government or community interests on an infrequent basis when no adequate civil airport is reasonably available."

"We want to make it very clear that there are a variety of options available for those needing to fly to the base," Wirfel said.

A spokesperson at the base told the Miami Herald that lawyers, journalists and Red Cross volunteers can fly to the base on the weekly military flight from Andrews Air Force base near Washington. Permission to take the flight must come from the Defense Department's Office of Military Commissions.

Lawyers of the detainees were outraged by the decision.

"Though the military has started acknowledging that more prisoners are striking, we are being denied the ability to meet with them and see the true extent of what's happening there," according to a statement from lawyers representing an Afghan detainee named Obaydullah, who they say has lost 30 pounds since starting his hunger strike.

Lawyers from the firm Hadsell Stormer Richardson & Renick told CNN they had DoD approval for a meeting with Obaydullah next week but were told that the scheduled flight has been canceled.

"We are very concerned that the commercial flights have ended at a time when it's critical to have more regular contact with our clients (not less!) in light of the hunger strikes and their potentially perilous health conditions," Ranjana Natarajan, one of the lawyers representing Obaydullah, wrote to CNN.

Navy officials said lawyers and others who regularly take the commercial flights from Florida to the base may now take a once-a-week military flight from Andrews Air Force Base just outside of Washington.

But Anne Richardson, also with Hadsell Stormer Richardson & Renick, said the flights "are also capable of being canceled, at the last minute, without warning and at DOD's discretion."

David Remes, a Washington-based lawyer who represents 15 clients held at the detention facility, said authorities "are canceling these flights because they want to keep the public in the dark about the mayhem in the prison."

"For the past several months, bad news has been streaming out of the camps," Remes said. "The authorities are taking one hit after another for the way they're running the camps, so they're doing what comes naturally -- choking off the flow of information."