I pay spousal support to my ex-husband. He was disabled during our marriage and the judge ordered him indefinite spousal support in 2005. We were married for 12 years. I recently found out that his parents are providing "over half- the support for his household". He lives with them. It is my belief they may actually be claiming him as a disabled dependent. This is do to a statement in an email he sent me stating that he was filing single, but claiming our college age daughter as a dependent. He says he can't file head of household under the tax stipulations, because they support the household.
So, my questions are:
Is there a California Law or statute that I could use in order to be able to stop paying him spousal support, considering they are supporting him?
Also is there a way I can get the parents' tax records to prove they are claiming him as a dependent and possibly even my daughter as one as well?

For 1 thing your mixing up concepts. The spousal support is for maintanence of your spouse( ex ). You might be able to modify it but to stop it doesn't sound correct. Being set aside is a slim chance at best. The reason he has to prepare a tax return is because spousal support is a taxable item. If he is making over the minimum then he is required to file.

I pay spousal support to my ex-husband. He was disabled during our marriage and the judge ordered him indefinite spousal support in 2005. We were married for 12 years. I recently found out that his parents are providing "over half- the support for his household". He lives with them. It is my belief they may actually be claiming him as a disabled dependent. This is do to a statement in an email he sent me stating that he was filing single, but claiming our college age daughter as a dependent. He says he can't file head of household under the tax stipulations, because they support the household.
So, my questions are:
Is there a California Law or statute that I could use in order to be able to stop paying him spousal support, considering they are supporting him?
Also is there a way I can get the parents' tax records to prove they are claiming him as a dependent and possibly even my daughter as one as well?

You need to go back and look at your judgment under which the court ordered you to pay spousal support. Did the court take into account that he was living with his parents or that they were partially supporting him? If so, then you have no basis (no change of circumstances) for modification of the support order. If his living with his parents and them supporting him (at least in part) is something new (post-judgment) then yes, you probably could move to modify, but probably not terminate, support. You would simply treat the value of the support his parents provide as non-taxable income to him in re-evaluating the support award. There is no statute that would simply allow you a termination under the facts you've stated.

If you try to subpoena the parents' tax return they could avoid having to produce them because they are subject to a privilege and non-discoverable. Apart from that they are of doubtful relevance.