Houston: A new law has come into effect in US' Texas state that allows students to carry guns onto the campuses of public universities across the state. The new Campus Carry Law, passed in 2015, went into effect on Monday, CBS News reported. The state's controversial law allows students who are at least 21 years old and who have a concealed handgun license to carry their guns at all public colleges and universities. Some college facilities, including sports arenas and chemical labs, are off-limits for concealed gun holders while private schools and two-year community colleges are excluded until next year, when the law takes effect at those schools, reports NBC News. The law took effect on the 50th anniversary of the clock tower massacre, in which a student gunman shot 49 people, killing 16, at the University of Texas at Austin on August 1, 1966. The shooter, Charles Whitman, a Marine-trained 25-year-old engineering student, climbed to the 28th-floor observation deck of a campus clock tower and began firing on students and staff. The massacre is one of the deadliest mass shootings in American history, NBC News reported.