Mr. Volokh is mistaken about Louisiana law. He states "Louisiana law in effect prohibits carrying by 18-to-20-year-olds within one thousand feet of a school or university..."
I believe here he refers to the CC permit which cannot be obtained until the age of 21. However, the Louisiana gun free school zone law provides an exception to constitutionally protected activity. Open carry is constitutionally protected in this state. 19 to 20 yr olds have the right to OC in a state gun free school zone.
It's good that people are still looking at getting rid of this ridiculous unconstitutional law.