In order to call yourself a REALTOR® you must be a current member of the National Association of REALTORS® (NAR).
NAR does not issue real estate licenses so you cannot ever be a "licensed REALTOR®" because there is no such thing. States issue real estate licenses, not NAR.
Being an NAR member entitles you to call yourself a REALTOR® but it also carries an obligation to use the word correctly, both in advertising and Internet usage.
A. REALTOR® Members are licensed to use the following MARKS:

An easy test to apply to see if you're using the word properly and in context is to simply substitute the word "member" for "REALTOR®" and see if what you're saying makes sense.
For example I see lots of people wanting to be "Your REALTOR® for life." Does "Your member for life" make sense to you???
Lots of licensees want to be "The neighborhood realtor". Not only can they not use the word properly they're saying they want to be "The neighborhood member".
Some licensees buy domain names saying "www.World'sGreatestRealtor.com. Can't do that; NAR's trademark usage policy says in any sort of advertising, internet included, you can only use the "R" word with a current NAR member's name or their firm name. No other usage is proper or allowed.
NAR has a whole trademark enforcemark enforcement department dedicated to keeping the "R" word usage correct. You can report any suspected or blatant violations to Trademark@Realtors.org (you need to use the "s" after "Realtor" for it to go through. In just a few days you will probably get an e mail from a very nice lady named Mary Newill thanking you for alerting her department to the problem and telling you they are on it.
If you have any questions or concerns about proper usage of the "REALTOR®" word visit http://www.realtor.org/ to find out what to do as well as what you and other NAR members shold not be doing.
I've never understood why this is such a hard thing to figure out, although I am just as guilty of it as the next. Saying my career is REALTOR® makes sense to the public but is not correct. I am a real estate agent which is a mouthful! Much like not being able to use MLS in websites in our area, the public doesn't know so continues to misuse the terms. The only people who are being prevented from use are the members! Ironic.