The basis for the suit would be that Navarro's election to the San Bernardino Valley Municipal Water District board makes him ineligible to simultaneously serve on the county school board because of a conflict between the offices.
"We find that there is a substantial issue as to the incompatibility of the two offices Mr. Navarro currently holds, because we have previously found similar offices to be incompatible," reads a June 11 letter from Susan Duncan Lee, supervising deputy attorney general. "A suit ...is the appropriate forum for resolving the issue."
Navarro says the two positions don't conflict with each other and that voters should decide whether he can hold both.
"It's a shame that Dr. (Gary) Thomas, our superintendent, wants to spend taxpayer dollars recklessly," he said.
Navarro has been holding fundraisers to pay for his defense, but he said Friday that he also will ask to have the county pay to defend him as an elected official - despite the fact that the county is the one trying to remove him.
Navarro, who has served on the county school board since 2006, was elected to the water board on Nov. 6.
In December, attorneys for San Bernardino County concluded there is a potential conflict of interest in Navarro holding the two seats simultaneously, partly because the water district sets wholesale rates that could indirectly be passed to the county schools office.
In February, the school board voted to leave him in place until the state Attorney General's Office weighed in.
"A significant clash of duties may arise in such matters as the Water District setting the wholesale water rate that will be passed on to the (county schools office) by the retail water agencies involved, determining the need for restrictions on water usage during times of water shortage," Deputy County Counsel Carol A. Greene said in a February letter.
Greene was quoting a 2002 decision by the Attorney General's Office concerning another school district and another water district.
If there is a "significant clash of duties," the official must resign the position they first held.
County spokesmen were not available to comment Friday afternoon.