from fastapi import APIRouter, HTTPException

router = APIRouter()

states_in_france = [
    "Auvergne-Rhône-Alpes",
    "Bourgogne-Franche-Comté",
    "Bretagne",
    "Centre-Val de Loire",
    "Corse",
    "Grand Est",
    "Hauts-de-France",
    "Île-de-France",
    "Normandie",
    "Nouvelle-Aquitaine",
    "Occitanie",
    "Pays de la Loire",
    "Provence-Alpes-Côte d'Azur"
]

@router.post("/france")
async def get_states_in_france():
    """endpoint that returns list of states in france"""
    if request.method != "POST":
        raise HTTPException(status_code=405, detail="Method Not Allowed")

    return {
        "method": "POST",
        "_verb": "post",
        "states": states_in_france
    }
```

This code defines a FastAPI endpoint at `/france` that responds to POST requests. It returns a JSON response containing the list of states in France, along with the HTTP method used ("POST") and a special "_verb" field set to "post".

If a request is made with a method other than POST, it raises an HTTPException with a 405 Method Not Allowed status code.

The list of states is stored in the `states_in_france` variable at the top of the file.