Actually, the IEP team is responsible for deciding accommodations and goals and monitoring progress in goals.
Let's see...you go into an IEP meeting; you have a group of people sitting there. There is usually an administrator, in the form of a priniciple, you have a regular classroom teacher, you have a special ed teacher, and an SLP that works for the school system. Then you have a parent. How do you figure that you are a 50% stakeholder?
Yeah, you can refuse changes in the IEP. Then it goes to due process. Depending upon your reasoning for not signing off, you have a greater chance of loosing in due process than in winning. The school system has lawyers on retainer just for these cases. In the meantime, your child remains in that school under the IEP as written without your signature, or you move and put the child in another district, which invalidates the IEP and you start the process all over again.