There are numerous pitfalls that may arise whenever any other party is allowed to use your mark.
REGISTERED TRADEMARK 3,432,286
The same mark can be registered with the U.S. Trademark Office by different parties for different goods or services as long as consumers are unlikely to be confused by the different uses.
While it is not illegal to allow (i.e., license) someone else to use your mark, there are numerous pitfalls that may arise whenever any other party is allowed to use your mark.
Unless you have a nationally recognized, famous mark that could raise significant revenue from licensing other goods and services to use the mark, the best approach is to avoid allowing any other party to use your mark. In any event if you believe the circumstances may merit further consideration, seek advice from an experienced trademark attorney.