12:44 PM -- The news conference has wrapped up. Meek spoke for several minutes and underscored the need to change the criminal justice system. He championed the cause by helping introduce House Bill 1925, which has bipartisan support.

Meek, who is still on probation, said there's a lot of statutes and laws that don't make sense ... and he's there to give the voiceless a voice.

Meek Mill's mission to reform the criminal justice system will take a huge step when he introduces a new bill at a news conference slated to begin at noon ... and TMZ will be streaming live.

The rapper will be flanked by 76ers co-owner Michael Rubin, CNN's Van Jones -- who is also the CEO of REFORM Alliance -- and several local politicians at the Philadelphia Municipal Services Building ... where they'll propose new legislation to reform the state probation and parole system.

The proposed bill aims to prevent the courts from sentencing a person to consecutive probation sentences, prevent the court from extending a person's time on probation or parole due to nonpayment of fines and fees, plus establish a system of incentives that reward good behavior.

As you know ... Meek's been pushing for reforms to the criminal justice system all over the country since he was locked up for more than 5 months on a probation violation. He helped launch REFORM Alliance with Jay-Z, among others, and they've vowed to get at least a million people out of jail over the next 5 years with a focus on probation and parole.

Meek calls this proposal the first step to changing the system in his home state. He also said, "I’ve lost too much time away from my son, my family, my friends and fans in Philly because of outdated probation laws, so I want to make sure people don’t have go through what I did.”