He says so-called TRT is only one problem and he wants to go even further than the ban.
"It's about time," St-Pierre told reporters at a promotional event in Montreal on Friday. "I think it's a good thing."
The commission voted unanimously in Las Vegas on Thursday to quit granting therapeutic use exemptions for fighters undergoing TRT.
"It's not the UFC (that's) the problem," said St-Pierre. "I believe it's the sport, the system."
St-Pierre added he thought the ban is a move in the right direction.
"I believe there's a lot more things to do. I believe they need to allow testing too — testing by an organization that doesn't have any interest in the money surrounding the fight."
St-Pierre said the decision by Nevada state regulators is "great for a lot of guys — good, honest guys will be happy."
The decision by the commission that regulates boxing and mixed martial arts in Nevada came several weeks after the Association of Ringside Physicians labelled so-called "unmerited testosterone'' a health risk for athletes who practise combat sports.
UFC president Dana White said he also supported the Nevada ruling and encouraged all athletic commissions to adopt the ban.
"We believe our athletes should compete based on their natural abilities and on an even playing field," he said in a statement.
White also said the UFC would honour the ruling in international markets, "where due to a lack of governing bodies, the UFC oversees regulatory efforts for our live events."
Several UFC fighters have been granted exemptions in recent years to use testosterone before their bouts, ostensibly for medical reasons.
The decision is already having effects on UFC. Vitor Belfort, who used TRT, dropped out of his upcoming middleweight title shot against Chris Weidman.
As for his own future in the UFC, St-Pierre wasn't telling reporters much, except to say that he's in the best condition he's ever been in his life.
The 32-year-old suffers from obsessive compulsive disorder and did not sleep much for about a decade.
"What's changed is that I'm sleeping better," he said. "Before I slept around five hours a night because of stress, but now I'm around seven hours and that's made a big difference in my life."
St-Pierre said he's living a more healthy lifestyle, the stress is gone and he's happier.
He took a break from UFC last December for personal reasons and still hasn't decided whether he will return to the octagon.
"I don't know if I'm going to stop," St-Pierre said. "I don't know what I'm going to do. I need a bit of time to decide what I'm going to do."
But he hasn't completely ruled out a career in the movies, after getting a small part as the villain Batroc the Leaper in the upcoming "Captain America: The Winter Soldier."
"I don't know if I'm ready to do that full-time," he said. "I don't know if I'm a good actor."
St-Pierre said he may have to come on as a bad guy in the ring, but that's what's necessary in his sport.
"I don't believe in bad persons," he said. "I believe people are shaped by their genetic environment.
"Some people say they look at a serial killer and say he's a bad person. He's not a worse person than you are because he had been shaped by his genetic and social environment and that makes him what he is — that's what I believe."
The former champ may have hinted at his future Friday as he spent almost an hour coaching a group of 18 enthusiastic amateurs in the finer arts of ultimate fighting.
The group included a number of winners of a cross-Canada contest by Bacardi Canada, one of St-Pierre's main sponsors.
— With files from The Associated Press
Follow @Peter_R_Space on TwitterSuggest a correction