By Trevor Hunnicutt WASHINGTON (Reuters) -U.S. President Joe Biden on Saturday signed into law the first major federal gun reform in three decades, days after a decision he condemned by the Supreme Court expanding firearm owners’ rights. “God willing, it’s going to save a lot of lives,” Biden said at the White House after signing the bill with his wife Jill by his side. The bipartisan bill came together just weeks after mass shootings in Uvalde and Buffalo that killed more than 30 people, including 19 children at an elementary school. The law includes provisions to help states keep guns out of…