A United Nations human rights expert is recommending changes in the way protests are handled in the United States, saying the process of issuing permits for demonstrations is “arbitrary” and could easily lead to discrimination against certain groups. Maina Kiai of Kenya, U.N. special rapporteur on freedom of peaceful assembly and of association, offered preliminary findings Wednesday from his visits this month to seven U.S. cities — including the sites of this year’s Democratic and Republican political conventions — to investigate how the U.S. upholds its citizens’ rights of assembly and association. Kiai’s full report to the United Nations will...