How are prisons and the military so different when it comes to free speech and expression?

There is limited free speech for military and according to first amendment there is free speech for the prisoners.

Explanation:

According to the first and fourteenth amendments of the US constitution it allows the citizens to express their opinion and ideas only up to a level or limitations. According to the amendments the prison and military is also adhered to free speech and expression.

The Supreme Court in its ruling as stated that prisoner can have contact with the outside world subjected to adhere to the internal security. It says that they can send and receive mails and have outside contact according the first Amendment.

But in military free speech is very limited and it has regulation under include the Uniform Code of Military Justice (UCMJ) and Defence Department Directives

Both the prisons and the military have free speech and expression under the First Amendment right has held by the U. S. Supreme Court, but these are limited under some circumstances.

Explanation:

Basically, all civilian population in the US have the right to free expression under the First Amendment.

For the Military, the U. S. Supreme Court has held that there is a limited level of free speech for members of the military. Although the service members have the same level of free speech and expression like the civilian under First Amendment rights, but this is limited because no military man is given the right to make any statement or publish any information that will put his unit or its cause in danger or at risk.

For the prison, the U. S. Supreme Court has held that under the First Amendment right, prisoners have the right to receive and send mail. However, this is limited only when there is a need to protect the security of the institution. This is because the First Amendment right does not give the prisoners the right to circulate information calling for a mass protest against mistreatment. The prison official are therefore empowered to discipline inmates who circulate such information.