Gov. Greg Abbott of Texas on Thursday pardoned a man who was convicted of fatally shooting a protester during a Black Lives Matter demonstration in the summer of 2020, fulfilling a promise he made last year amid pressure from conservatives.

The decision immediately followed a pardon recommendation from the state’s Board of Pardons and Paroles, whose members are appointed by the governor. Lawyers for the man, Daniel S. Perry, argued that he had acted in self-defense against the protester, who was carrying an AK-47-style rifle.

Mr. Perry was sentenced to 25 years in prison in an emotional hearing last year in which prosecutors presented evidence of racist online comments he had made and said that psychological experts had found him to be “basically a loaded gun.” As the pardons board considered the case, lawyers with the Travis County district attorney, José Garza, met with the board to argue against a pardon.

Under Texas law, a recommendation from the board is necessary before the governor can grant a pardon.

“Texas has one of the strongest ‘stand your ground’ laws of self-defense that cannot be nullified by a jury or a progressive district attorney,” Mr. Abbott, a Republican, said in a statement on Thursday. “I thank the board for its thorough investigation, and I approve their pardon recommendation.”

The case landed at the intersection of some of the most contentious issues facing the nation, including the protests over the killing of George Floyd, the proliferation of military-style rifles in the hands of civilians, and the legal rights of those who choose to stand their ground and open fire, rather than retreat, when they perceive themselves to be under threat.