The news release from American Oversight highlights the Freedom of Information Act requests that it is seeking to enforce, including these regarding the sovereign Tohono O'odham portion:
The communications include any contacts the federal government has had with the Tohono O'odham Nation or its lobbyists. The Nation has one of the largest lobbying contracts in Washington, although until recently, much of that was focused on the battle to open up the heavily contested casino west of Phoenix.
Here is the specific part of the Complaint dealing with the Tohono O'odham portion. (The rest of the complaint can be found here):