The Privacy Act section says that if you fail to put a valid leave address, your leave request is supposed to be summarily denied. Also, since your signature is on there, that makes it an official form - and if you lie on it, you CAN be (not mandatory, but you CAN be) charged under submitting a False Official Statement.
In addition to this, if you are looking to go to a foreign country, most countries need special permission to enter - and if you fail to get it, you can be charged with Failure to Obey a Superior Officer or Failure to Obey a Lawful Order.
Then, to top it all, if you get hurt while in a foreign country that you have no specific approval to visit, you can be held liable for any and all medical treatment you need... AND, if the unit calls to recall you and you can't be reached, you can be charged for the appropriate cites.
And like MRS JVB said, that wonderful clause in Article 134 can be added to the whole mess.