Ala. Code § 40-15-17

In the event that the estate of any decedent taxable hereunder shall include property situated outside of the state, the proportion of the federal estate tax leviable hereunder against or in respect to the property of the estate subject to the tax imposed hereby shall be that proportion which the property of the estate within or subject to the tax jurisdiction bears to the gross value of the estate of the decedent not so subject to taxation.