De Lima was jailed during the Rodrigo Duterte presidency after years of investigating drug-related killings.
De Lima faced various charges in 2017 within months of launching a senate inquiry into Duterte’s bloody anti-drugs campaign, in which thousands of users and dealers were killed by police or in mysterious circumstances.
Critics and rights groups said the police summarily executed drug suspects, which the police deny, saying they acted in self-defence.
Duterte, whose term ended in 2022, accused de Lima of colluding with drug gangs while she was justice minister.
“I am now completely free and vindicated. It’s very liberating,” an emotional de Lima told reporters as she emerged from the southern Manila courtroom on Monday, where the case against her was dismissed due to insufficient evidence.
“My heart is full with all the love pouring in today after the dismissal of all my cases,” she wrote in a post on X.
De Lima was arrested in 2017 while a sitting senator, and spent more than six years in jail while on trial for three drug-trafficking charges.
She was freed on bail in November last year, having earlier been cleared of the two other drug charges.
The final drug case that was overturned on Monday concerned the 2010-2015 period when she was justice minister, with allegations that she took money from inmates inside the country’s largest prison to allow them to sell drugs.
De Lima maintained that the charges, which carried a maximum penalty of life in prison, were fabricated in an effort to support the narcotics crackdown.
Multiple witnesses, including prison gang bosses, died or recanted their testimonies during the lengthy trials.
The court on Monday also dismissed another charge alleging de Lima pressured a former employee to ignore a 2016 summons issued by the House of Representatives for a hearing in relation to the trade of illegal drugs in Philippine prisons.
That case, the only other criminal proceeding against her, had carried a penalty of anywhere between a fine and six months in prison.
Amnesty International welcomed the dismissal of the “bogus charges” against de Lima in a statement, saying it was overdue after “nearly seven years of arbitrary detention, as well as relentless political persecution”.
Duterte is facing a probe by the International Criminal Court over the anti-drugs campaign. De Lima said on Monday that she will continue to help the court with its probe.