Unless otherwise specified in a contract, the graphic designer retains the right to his or her creations, and should always attempt to do so. When designing a work for a client, you are also selling specific rights to use it. Copyright laws protect against additional use without proper compensation or agreement.
For example: You design a logo for use on a specific product package for a cosmetics company. The company likes it so much that they decide to extend its use across their entire product line. You should be paid for this additional use, as it increases the value of the graphic work you created. For this reason, be sure to include in your contracts what the work can and cannot be used for.
“The Graphic Artists Guild Handbook: Pricing and Ethical Guidelines.” Eleventh Edition. Graphic Artists Guild, Inc. 2003.