Semi-automatic firearms have been popularly sold to private citizens since the late-19th century. They are the most-popular design sold today and have clear constitutional protections. So, no, the president doesn't get to tell us we can't own them.
The Second Amendment is in the U.S. Bill of Rights, but it is nevertheless legally perilous to travel around America with this right. Here is a guide for how to travel today and what needs to happen so we can better carry this freedom with us.