The Williams "case" isn't strong if you know the first thing about Physics (e.g. half-life of atomic elements).
Suitcase nukes are SMALLER than ordinary nukes.
The smaller the nuke, the shorter the shelf life.
The less shielding that you have, the sooner that your electronics and conventional explosives deteriorate from the radiation.
The less fissionable material that you have, the faster you generally need your atomic trigger isotopes to emit neutrons. The faster you emit neutrons, the shorter your half-life. The shorter your half-life, the less time that you have before the nuke simply fizzles instead of booms. Beryllium trigger isotopes can have as little as a 53 day half-life, for instance. Polonium 210, a Man-made isotope that can *only* be created in nuclear reactors or cyclotrons, has a 140 day half-life.
This is simple physics. Moreover, heavy metals like uranium and plutonium are among the most brittle materials known to man, and the slightest bit of humidity turns them into uranium oxide or plutonium oxide (i.e. worthless rust).
So a "suitcase nuke" from 1991 (the fall of the CCCP) is likely little more than a rusted, shattered, fragmented collection of wiring and explosives today.
They *require* a constant, highly professional level of maintenance that needs to be performed in very, very highly advanced clean room labs.
No maintenance means no "Boom."