sleepy,
This is similar to what my Junior High chemistry teacher told me. I believe he was basing his statements on Einstein's writings (he had a major jones for Einstein) when he said that "time is change." By that notion, if we could measure the smallest change, then the time it took for that change to occur is the smallest measurable unit of time. I can't remember, but I thought he said the smallest measurement of change was the vibration of electrons as they orbited the nucleus of an atom. That was many years ago.
Dunssco... uh, I mean, non_trias_theos might have the "obvious law" that bathory is looking for.
If I understand correctly, the "Planck length" is the distance scale at which gravity crosses over from the quantum to the 'classically measurable' and is about 1.6 x 10^-35* m or about 1 x 10^-20** times the size of a proton. Any distance under this is impossible to measure because you cannot accurately determine the position and momentum of a subatomic particle closer than this "Compton Wavelength." (Maybe this is the 'vibration' that my Junior High teacher was talking about. And I thought he was an idiot because he believed in evolution...)
"Planck time" is the time it would take a photon in a vacuum cleaner to travel that distance--about 1 x 10^-43*** seconds.
Hmmm
To get an idea of how small 1.6 x 10^-35 is, compare it to how large our sun is, which has a mass of 2 x 10^33 grams
* .00000000000000000000000000000000016 meters
** .000000000000000000001 the lenght of a proton
*** .00000000000000000000000000000000000000000001 seconds