Why won't my 2002 subaru Forrester let me pump gas into the gas tank

All vehicles have to vent the tank to fill, and those fumes from the tank must past through the charcoal canister and the canister could be saturated with fuel from over filling the gas tank(when re-fueling after the gas pump clicks OFF the FIRST time >STOP< fueling,don't try and fill it to the rim).Possible bad vent valve.Possible broken dry rotted,clogged vent hose with a thick, tough spider web, with a big fat mama spider with a sack of eggs attached to her.