I assume this is your son you are talking about. It is not clear from your answer exactly what happened 9 years ago, because Washington does not have "temporary" guardianships. Generally speaking whatever process you went through back then to give custody/guardianship to your mother, is the same process you will need to go through to get your son back. You may have intended it to be temporary, but a court may not see it that way.

For example, if it was a guardianship proceeding and the Order Appointing Guardian gives her the right to make medical decisions, etc., then you need to petition to terminate the guardianship. If it was a nonparental custody proceeding and a residential schedule was entered stating that your mother is the primary custodian, you will need to obtain a new Order naming you as primary cusdodian.

It's also possible that no court proceedings were held and you signed a Power of Attorney or similar document for your mother to use when dealing with the school and doctors. If so, and there is no court order to deal with, then you would legally have the right to simply revoke the document you signed and take your son back. However, if he has lived with your mother for 9 years, I would advise against removing him from her home until you meet with a lawery one-on-one and get more specific legal advice that could only be provided with much more information.

I say that because such action could backfire if you do end up in court, as a judge may not look favorably on you simply removing your son from what I assume is the only home he's known for the past 9 years, even if it's not in violation of any outstanding court orders.

If cost is a concern, check with your local bar association and see if they have any legal clinics or other services they offer on a free or sliding scale basis.

Whatever you do, the other parent's rights will probably need to be considered, unless he or she is deceased or parental rights have been terminated.

Talk to a lawyer in Washington (assuming that is where the guardianship proceeding was filed). If this is a court guardianship, it will take court action to terminate it. The good news for you: in many states such guardianships have to end once the parent withdraws consent, unless the guardian files a new proceeding in an attempt to show that the parent is unfit. If that is how Washington law works, you probably will not need an attorney to terminate the guardianship, and your mother probably will not pursue the issue.

All that said, please do keep in mind that the most important thing is your son's well-being. You being right is not necessarily the same as his best interests. I know you know that, but people do get caught up in the struggle and sometimes lose sight of the real goal. I'm sure you will not succumb to that temptation.