I've added an optional question during forum registration and to the "Personal Details" settings page. If you have never served, or you do not wish to disclose this information, you do not have to go to the page and change these settings.
The question(s) and description under the drop down menu explain the purpose of these settings.
To modify these settings go to your personal details page, select the options that apply to you and save your settings.
After the settings have been saved there will be a little something added under your avatar and on your profile page within 15 minutes.
Going on the honor system here, I won't be verifying anyone's settings/claims here, but if it somehow got out that some porky pies were being told restrictions may be placed on the offending user's account. (Though probably not.)