[weegee]

I don't know why some people are charged in the federal system rather than more lenient state systems; but the trends show federal rather than state drug charges are increasing steadily.

Could it be transportation across state lines (trafficking even small quantities or even carrying something illegal on a vacation?). Could it also include "involvement" in a criminal enterprise that operates within several states?

[ellery]

That can't be the criterion or there would not be people in federal prison for simple possession. The charts show that a number of people were suspected of simple possession ONLY, or possession of a certain amount ONLY.