US First Amendment law is quite complex, and there's a lot of annoying little details to consider.
Essentially, designating a public forum means that the only restrictions are "time, place, and manner", and restrictions must be content-neutral. Furthermore, even the time/place/manner restrictions have to follow some level of reasonableness, with the exact level dependent on mildly arcane details, and I don't know the exact details here. The safest thing to do is say that he can't block trolls, because it's always easiest to default to assume that blocking speech is unconstitutional.
First Amendment rights are surprisingly far-ranging--it's unconstitutional for a city to deny neo-Nazis the right to march in a neighborhood of Holocaust survivors.
Essentially, designating a public forum means that the only restrictions are "time, place, and manner", and restrictions must be content-neutral. Furthermore, even the time/place/manner restrictions have to follow some level of reasonableness, with the exact level dependent on mildly arcane details, and I don't know the exact details here. The safest thing to do is say that he can't block trolls, because it's always easiest to default to assume that blocking speech is unconstitutional.
First Amendment rights are surprisingly far-ranging--it's unconstitutional for a city to deny neo-Nazis the right to march in a neighborhood of Holocaust survivors.