While there are a number of different types of exclusivity agreements, I assume that you are referring to an agreement under which your client would agree to work exclusively with you or obtain your type of services exclusively from you.
If thats the case, then such an agreement should be enforceable, although you need to be careful that this agreement doesnt constitute a non-competition agreement, since those types of agreements can be problematic in certain states, especially California.
Question added to topic Legal Basics For Startups • September 12, 2007
Is an exclusivity agreement enforceable by law?
Can I ask my client for an exclusivity agreement?
Mark L. Skaist is a shareholder in the Newport Beach office of Stradling Yocca Carlson & Rauth, where he specializes in corporate and securities law.