From this:

Amid cheers from supporters, marijuana advocate Ed Rosenthal was sentenced on Wednesday to a single day in jail for growing the drug in violation of federal law even though California allows its cultivation for medical use.
U.S. District Judge Charles Breyer said he handed down the light sentence because of the "extraordinary circumstances" of the case -- referring to the fact that growing marijuana for medical purposes was legal under a voter-approved California law...

Breyer sentenced Rosenthal to a single day in prison but gave him credit for time served so he walked out of court a free man. He also fined Rosenthal $1,300.