The man who can't be trusted with Twitter has the nuclear codes

In a letter to her Democratic House colleagues on Friday, [House Speaker Nancy] Pelosi said that she had spoken with the chairman of the Joint Chiefs of Staff, Gen. Mark Milley, about "available precautions for preventing an unstable president from initiating military hostilities or accessing the launch codes and ordering a nuclear strike."

"The situation of this unhinged President," Pelosi wrote, "could not be more dangerous and we must do everything that we can to protect the American people from his unbalanced assault on our country and our democracy."

Pelosi later told her caucus she had received assurances that there were safeguards in place, according to a source on the call. It is unclear what those safeguards might be.

Separately, several senators and members of Congress have written to Milley and acting Defense Secretary Christopher Miller to put checks on the president's authority to launch nuclear weapons.

Under current rules, Trump is the only person in the government who can order a nuclear strike.

[...]

Under the current setup, the president travels with what is known as the nuclear "football," a briefcase that would allow him to initiate a nuclear strike from anywhere and at any time. The contents of the football are unknown, but it's believed to contain a phone and a number of predesignated attack options, says Joshua Pollack, a senior research associate at the Middlebury Institute of International Studies at Monterey.

The system was designed at the height of the Cold War when some feared a president would have just minutes to respond to a massive, incoming Soviet attack.

[...]

The checks and balances in place are designed to authenticate the president and relay his orders reliably to the military. But the whole command structure "just assumes that the president is fit for the job and is not going to arbitrarily order a nuclear attack," Pollack says.

In practice, Pollack says, it would probably be somewhat hard to start a nuclear Armageddon. Under most imaginable circumstances, senior Pentagon officials would be in the loop, authenticating the president's orders and advising him on what actions to take. If they feel the order is unlawful, they can refuse to carry out the launch.

But Pollack believes that by using the predesignated strike options in the nuclear football on his own, a president can technically bypass that system.

  NPR

Perhaps they could change the code?  Perhaps they already did - three or so years ago - without his knowledge.

...but hey, do what you want...you will anyway.