By Kanishka Singh WASHINGTON (Reuters) – The U.S. Justice Department on Wednesday filed a lawsuit against Texas to challenge an immigration law that gives state officials broad powers to arrest, prosecute and deport people who illegally cross the U.S.-Mexico border. WHY IT’S IMPORTANT The law, known as SB4 or Senate Bill 4, makes it a state crime to illegally enter or re-enter Texas from a foreign country and gives state and local law enforcement authorities the power to arrest and prosecute violators. It also allows state judges to order that individuals be deported, with up to 20-year prison…