根据

According to This post, it is not possible, you would have to do something like:

[OperationContract]
[WebGet(UriTemplate = "people/driversLicense/{driversLicense}")]
string GetPersonByLicense(string driversLicense);

[OperationContract]
[WebGet(UriTemplate = "people/ssn/{ssn}")]
string GetPersonBySSN(string ssn);