How come when Sarah Palin does an interview, your not allowed to ask her follow up questions?

Theres a clause in her contracts that they aren't allowed to ask her follow up questions? After the Katie Curic interview, Palin has made it really hard for reporeters to probe her message or get details for her plan for the country. How would a voter make an informed decision about her, when she never goes into details about anything she has planned.