Can I wear a Military Jacket?

You are certainly allowed to wear the uniform, as long as it's not identifiable as a particular soldier's uniform. For example, a military wife can not take pictures in her husband's uniform top as a gift while he's deployed. That is unacceptable, and punishable, even if they are in good taste. The garment must be stripped of all recognizable insignia. But even then, a civilian could not get in trouble for it, only the military member.