For lawmaker Jan van Aken, little symbolizes more potently all that he finds indefensible about Germany’s arms exports than the German and French-made anti-tank missile that he was shown in northern Syria.

From its serial number, he believes the 1970s MILAN rocket was sold legitimately by France to then Syrian leader Hafez al-Assad. After decades in a depot, it fell into the hands of al Qaeda-linked militants in the uprising against Assad’s son Bashar.

Earlier this year, the German politician examined the waist-high green tube left after the missile was fired at the Kurds. […]