What? Right turns being generally permitted on red (after stopping, while yielding to traffic that has the right of way) does not mean you "cannot prohibit right turns under any circumstances"-- there just needs to be a sign prohibiting them (or a red right arrow means the same-- you may not turn right while it's lit, although around here you'll usually see that paired with a sign because people are stupid).

Cases where it's prohibited are plentiful, usually in cases where a right on red can't be executed safely (like if there's poor visibility around a corner) or if right on red would be disruptive to traffic flow.