The American military services believe in tradition, but they are increasingly recruiting troops from a population that is less interested in that sort of thing. In fact, the last few generations have adopted lifestyle customs that are quite at odds with what is thought of as a "military bearing" (how troops look and move). So all the services are increasingly adding rules stipulating how the troops should behave. Tattoos (where they are), piercings (very few), cell phones (how they are carried) and umbrellas (when they are allowed) have all been covered. But now the U.S. Marine Corps has come out with a new bunch of regulations, some of them making official what had long been unofficial custom. Just to make sure the young marines get the message.
A big issue is jewelry. The trend has been towards more, especially with the women. All the services have men and women in the ranks, and marines have now mandated that you may only have one ring per hand. But the custom of wearing gold or platinum caps on teeth is out, although waivers are available for those who have permanent caps implanted before October, 2007. Also forbidden is chest hair protruding from T-shirts. This one is a bit odd, since the U.S. Air Force has encouraged that sort of thing (but not made it mandatory.)
There are a lot of new rules about how you cannot cut your hair. No sideburns that end in a point (popular among civilians for over a decade) and exotic cuts for men or women. That means no Mohawk cuts (although this was popular among combat troops during World War II). Also outlawed are spiky hair, dreadlocks or anything that offends your gunny (Gunnery Sergeant, usually a platoon sergeant). The new rules do make it official that male marines can shave their heads, but female marines must have at least quarter inch (7mm) length hair. If the female marines have hair that extends below the collar, they must be able to put it up in a bun while on duty. The women do catch one break, in that patterned fingernails (French manicures) are now officially allowed.
All marines are now prohibited from putting their hands in the pockets (except to fetch something) while on base. If you are in combat and its cold, you can stick your hands in your pockets to keep your trigger finger limber. You are also forbidden from walking and drinking at the same time, something which has become common as more people carry a container of water around with them all the time.
Some of these items, like gold teeth, will now keep you from enlisting at all. This follows a program, that is already three years old, that prohibited anyone with certain types of tattoos from joining. This rule did not ban all tattoos, just those that would be visible while in their PT (Physical Training) uniforms (gym shorts and T-shirt).
This prohibition was odd, as tattoos have long been a favorite form of self-expression among military personnel. But since the United States eliminated conscription three decades ago, the brass have been less tolerant of recruits with lots of tats, especially visible ones. The USMC crackdown has a lot of do with the marines making their recruiting numbers more easily of late. They now have to find ways to decide who to accept, and who to reject. Folks with an abundance of tattoos are not welcome. The army, however, has loosened up on tattoos, and will probably get some people the marines turned away just because of the body art.
Until 2006, the Department of Defense paid for laser tattoo removal treatments. Since then (when more recruits came forward) troops have had to pay for it themselves, as do those potential recruits who have more tats than the recruiting rules allow. It's unclear why the brass at the Pentagon are so hung up on tattoos.