A 63-year-old New Orleans man convicted five years ago of knifepoint sexual assaults on two women in the early 1990s won’t be subject to a judge’s order for chemical castration because the law prescribing the procedure wasn’t around when he committed the crimes, the Louisiana Supreme Court ruled Tuesday.

The state high court also struck down convictions against Herbert Nicholson Jr. on counts of sexual battery, aggravated oral sexual battery and attempted aggravated rape.

Nicholson isn’t going anywhere, however. The Supreme Court maintained his three life sentences on two counts of aggravated kidnapping and a count of aggravated rape in separate attacks on female victims in 1991 and 1994 — crimes linked to him through DNA testing that came much later.

On the lesser counts, which carried terms of decades behind bars on top of the life sentences, the court found that the statute of limitations still applied at the time of the rapes, and that it had run out. The court found that those time limits still applied, despite a 2003 state law that retroactively reset the clock in cases where DNA testing uncovers perpetrators of long-ago sex crimes.

The court also found that chemical castration for some sex offenders — endorsed by the state Legislature in 2008 — amounts to additional punishment. That means a constitutional ban on ex post facto criminal punishment — punishment authorized after a crime was committed — applies, the court ruled.

Orleans Parish District Attorney Leon Cannizzaro’s office had argued that the chemical castration law was a remedial regulation, similar to sex offender registration requirements. A spokesman for Cannizzaro’s office declined to comment Tuesday, saying he hadn’t yet read the ruling.

The opinion, delivered by the court as a whole, signals that other convictions on sex crimes that aren’t punishable by life in prison can’t stand if the time limit for prosecuting them ran out before the DNA exception took effect 12 years ago. That could potentially affect several cases, such as Nicholson’s, that have cropped up from a push several years ago to test stacks of rape exam kits that had sat dormant for years or even decades on evidence room shelves.

In New Orleans alone, police in recent years have tested about 800 rape kits dating back to the late 1980s that had gathered dust, leading to several dozen matches. Just how many convictions stemming from those matches might be vulnerable under the court’s ruling was not immediately clear.

The greater impact on Nicholson, and perhaps others, is that the ruling indicates that nobody convicted of crimes committed before the 2008 chemical castration law took effect can be sentenced to the medroxyprogesterone acetate treatment.

Ben Aguinaga, an LSU Law Clinic member on a student team that litigated Nicholson’s appeal, said it’s uncertain how many sex offenders in the state prison system are subject to the controversial procedure.

“It’s a really drastic measure you certainly want to be careful about,” Aguinaga said. “One of the implications of this ruling is that this was a statute that wasn’t on the books until 2008, and it will only take effect on those people who have actually committed crimes after 2008.”

Justice Scott Crichton issued a separate, concurring opinion saying that, aside from the retroactivity problem, chemical castration for Nicholson “would otherwise be eminently reasonable and warranted based on this offender’s egregious and outrageous set of crimes.”

Criminal District Court Judge Robin Pittman handed down the sentences to Nicholson after a trial in which jurors heard evidence of even earlier assaults, from the 1970s, to which Nicholson had pleaded guilty, according to a nola.com report from 2010.

In another case, the story said, he’d been sentenced to death in the rape of a young girl, but the conviction was overturned. According to the report, Nicholson told Pittman to “rot in hell and suffer” following his sentencing.

Craig Mordock, one of Nicholson’s trial attorneys, said the legal questions addressed by the Supreme Court were raised early on in the case.

Mordock took broader issue with a law that allows a judge to sentence a defendant to chemical castration treatment on a first conviction for aggravated rape, forcible rape, second-degree sexual battery, molestation of a juvenile under 13 or aggravated crime against nature. The law mandates the sentence for a second offense.

“A person’s right to procreate is fundamental to their existence,” Mordock said. “The idea that the state Legislature wants to inhibit this, even on felons, means there’s virtually no limit to doing something like this.”

Follow John Simerman on Twitter, @johnsimerman.