President Donald Trump said Friday he is considering a pardon for the late heavyweight boxing champion Muhammad Ali, who died in 2016 — despite the fact that Ali's conviction for refusal of military service was overturned in 1971.Trump told reporters Friday that Ali is on a list of 3,000 people he is considering for pardons because, in his words, they "really have been treated unfairly."Ali's attorney, Ron Tweel, thanked the president, but noted that a pardon was not necessary. He told NBC News: "We appreciate President Trump's sentiment, but a pardon is unnecessary. The U.S. Supreme Court overturned the conviction of Muhammad Ali in a unanimous decision in 1971."Ali — who changed his name from Cassius Clay when he converted to Islam in 1964 — said his refusal to be drafted in 1966 was based on his religious beliefs and his opposition to the United States' involvement in the Vietnam War. Ali was arrested and convicted in federal court in 1967 for violating selective service laws. He was stripped of his boxing titles and license and fined $10,000. He faced a five-year prison sentence, but was allowed to remain free while appealing the decision. During the four years in which he could not fight, he was a social activist, speaking out against the war and in favor of racial equality.In 1971, the U.S. Supreme Court overturned Ali's conviction in a unanimous decision, accepting Ali's argument that he should be excused on religious grounds. His license to fight was also reinstated and Ali spent the next 10 years fighting professionally, cementing his reputation as one of the country's most prominent athletes.In 1977, President Jimmy Carter, on his first day in office, issued a blanket pardon for all of the hundreds of thousands of U.S. men who evaded the draft during the Vietnam War. Had the 1971 court action not already cleared Ali's name, experts say, the Carter decision would have done so.A presidential pardon does not render a person legally innocent of a crime, but it can clear the way for living pardon recipients to regain civil rights usually denied to ex-felons: the right to vote, to run for office, to serve on a jury, and to own a firearm, among others.A pardon for the deceased can provide no such reinstatement of rights and thus is seen as merely symbolic. The U.S. Department of Justice says, in general, it does not accept applications for posthumous pardons because its time can be better spend on living persons.But it notes that it has granted three posthumous pardons in recent years, in response to requests by President Bill Clinton, President George W. Bush, and Trump, who last month pardoned boxer Jack Johnson, who died in 1946.