He's without a doubt left a lasting impact on the law and the justice system as a whole, here's a quote from the WSJ showing this
But in his impact on American life, few jurists could match Justice Stevens’s legacy, which stretched from the living room—he wrote the decision establishing the consumer’s right to record television programs—to the frontiers of presidential power, including two seminal opinions curbing George W. Bush administration claims that it could imprison and punish detainees at Guantanamo Bay without congressional authorization or judicial oversight.