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 endpoint follows the provided rules and examples:

- It uses the `@router.post` decorator for the `/france` path.
- It validates that the request method is POST, otherwise raises a 405 Method Not Allowed error.
- The response includes the "method": "POST" and "_verb": "post" fields.
- The response contains a list of states in France under the "states" key.
- The code structure, imports, and naming conventions match the examples.