Requires that anyone affiliated with any terrorist organization who is found guilty of specified terrorist activities, if such an offense was committed pursuant to the advocacy or direction of such organization, be sentenced to a term of imprisonment in addition to that provided for such offence. Stipulates that the additional term of imprisonment shall be for not less than two years or more than ten years.

Directs that the defendant be sentenced to death if the death of any person occurred during the commission or attempted commission of such an offense.

Requires, if a defendant is subject to the death penalty under this Act, that the judge conduct a separate sentencing hearing to determine the existence or non-existence of enumerated mitigating factors. Reduces the additional sentence to a term of four years to life imprisonment if any such mitigating factor is found to exist. (Adds 18 U.S.C. 880-881)