If you are in the US, you should know that there is not a uniform set of codes, laws or ordinance governing cemeteries. There are hundreds or possible thousands of abandoned/unmaintained cemeteries of US government lands all over the country.
Some states have laws preventing the destruction (by intention ) of any cemetery while others do not. Local jurisdictions also have varriable laws or ordinances, and even when a historic cemetery comes into the local jurisdiction, there may be no rule that requires them to do regular maintenance. Sometime, it just means a yearly ride through with a bushhog mower or they just spray the whole place with weed killer.
If the cemetery is important to you for family or local history, you might try to see if the government agency is under any kind of maintenance requirement. Also, your local historical society might have knowledge of the location and its burials. Without an active advocate or cemetery association, not much will be done to help or save these kinds of cemeteries.