The California legislature passed SB 239 in September.
The law previously punished people who intentionally exposed or infected others with HIV by up to eight years in prison. The new legislation will lower jail time to a maximum of six months.
The new law will also eliminate the penalty for knowingly donating HIV-infected blood. This action is a felony under current law and will be decriminalized starting in January. Supporters of the change argue the previous law was antiquated because all donated blood is tested for HIV.
"The most effective way to reduce HIV infections is to destigmatize HIV," Wiener told CNN. "To make people comfortable talking about their infection, get tested, get into treatment."
Gloria released a statement Friday saying the bill will put the state "at the forefront in the fight to stop the spread of HIV."
Wiener said by destigmatizing HIV, the bill would encourage people to get tested, which will in turn lower HIV transmission in the state.
The governor did not respond to a CNN request for comment.
Opposition to the bill
Many Republicans staunchly opposed SB 239, saying it could lead to an increase in HIV infections.
Sen. Jeff Stone voted against the bill and strongly expressed his disapproval in September when the Senate voted on it.
Stone, who is also a pharmacist, took aim at Wiener and Gloria's argument that modern medicine can lower the spread of HIV. The senator said three out of four people who are on prescription medication in the United States do not comply with their doctor's orders on how to take it.
"If you don't take your AIDS medications and you allow for some virus to duplicate and show a presence, then you are able to transmit that disease to an unknowing partner," Stone said on the Senate floor.
Stone asked Brown to veto the bill in a letter obtained by CNN. The senator doubled down on his claim that "many people do not properly adhere to their drug treatment." Stone also wrote that the bill "runs contrary to the state's responsibility" of protecting Californians.
Sen. Joel Anderson, another Republican who voted against the bill, argued that people infected with HIV could never live their lives "to the same extent" again. He said it was irresponsible not to disclose the possibility of a life-altering infection.
"The critical word in this is 'intentionally,'" Anderson said in September. "When you intentionally put others at risk, you should have responsibility."
Organizational and LGBT support
The bill enjoyed support from Californians for HIV Criminalization Reform (CHCR), a coalition of several organizations, including the ACLU of California, whose mission is to replace the "stigmatizing laws that criminalize HIV status."
Rick Zbur, executive director of Equality California -- one of the organizations in the coalition -- told CNN his group was "elated" that the governor signed the bill and changed the state's "archaic laws."
"This is an important bill that modernizes California's HIV laws," Zbur told CNN. "It will really advance public health and reduce stigma and discrimination that people living with HIV have suffered."
The Los Angeles LGBT Center also supported the bill. The organization's director of government relations, Aaron Fox, told CNN the new law will see HIV-positive people "treated fairly under California law."
CORRECTION: An earlier version of this story inaccurately described the language of the current law regarding the intent to transmit HIV. The story also incorrectly described the change in penalty for knowingly donating HIV-infected blood. The penalty has been eliminated under the new law.