SAN FRANCISCO — Ed Rosenthal, the self-proclaimed “guru of ganja,” was convicted again Wednesday in federal court of illegally growing hundreds of marijuana plants that he said were meant to treat sick people, which state law allows.

Rosenthal was convicted of three cultivation and conspiracy charges after U.S. District Court Judge Charles Breyer prohibited the marijuana activist’s lawyers from telling the jury Rosenthal was working for a pot club sanctioned by Oakland government officials. The decision underscored the tension between federal law and laws in 11 states that have legalized pot to some degree.

“We weren’t allowed to give the jury valuable information it needed to make a fair and unbiased decision,” Rosenthal said outside court after the verdict was read. He was convicted on three felony charges and acquitted of one. The jury couldn’t decide a fifth charge.

Federal prosecutor George Bevan declined comment after the verdict was read.

The U.S. Supreme Court has ruled that marijuana is an illegal drug and federal law trumps state laws, which left Rosenthal without much of a defense. The jury deliberated for about two days before convicting Rosenthal of growing more than 100 marijuana plants, conspiring to cultivate the drug and maintaining a growing operation in a warehouse, but the 63-year-old won’t serve any time in prison.

That’s because Rosenthal was previously convicted of the same charges in 2003 and sentenced to a day in prison because the judge said that Rosenthal reasonably believed he was immune from prosecution because he was acting on behalf of Oakland city officials.

An appeals court tossed out that conviction because of juror misconduct. The judge, in a fruitless attempt to persuade federal prosecutors to drop the case, has said he would not sentence Rosenthal to any more prison time.