He was freed a day after the Lahore High Court declared his detention illegal.
The Punjab government last month detained Lakhvi before he could be released from jail after a court ordered his release.
Earlier, he was granted bail by an anti-terror court in December, which infuriated New Delhi and the government quickly slapped him with a detention order under the “Maintenance of Public Order” law.
The Islamabad High Court suspended that order, but the Supreme Court restored it in January.
Last month, the high court again set aside the detention order, saying government lawyers had failed to provide evidence to justify Lakhvi`s detention.
The accused was arrested in Pakistan in 2009 in connection with the attack on Mumbai by militants in which 166 people were killed. The sole surviving gunman had allegedly identified him as the mastermind.