Mr. Morant is facing a possible life term in the marijuana case.
Mr. Vines, who prosecuted one of the largest marijuana cases in California history and says he opposes recreational use of the drug, was pleased by yesterday's decision.
The substantive due process argument is sometimes used in medical marijuana cases.
The outcome of the marijuana case had been expected.
The marijuana case "does not necessarily mean a retreat," he said.
"The pattern was that marijuana cases were generally made in the Southeast - in Florida, Texas and the Gulf Coast."
The marijuana case was dropped after a friend came forward and claimed ownership.
In 1986, a jury convicted Mr. Nixon of lying to a grand jury when he denied discussing a marijuana case with a district attorney.
The marijuana case had an important constitutional overlay the power of Congress to regulate interstate commerce was at stake.
"I thought if I didn't, I'd be trying nickel-bag marijuana cases."