Constraint consequentialists believe that you should try to do good things that improve the world, unless those break hard-and-fast rules ("deontological bars").

For example, you shouldn't assassinate democratically-elected leaders, even very bad ones. Why not? Since bad leaders set bad policy, and bad policy can kill many thousands of people, wouldn't it be for the greater good? Because there's always one gun-owner who thinks any given leader's policies are bad, so without the rule, every leader would face constant assassination attempts, probably some of them would succeed, and the nation would either crumble or degenerate into a security state.

This explanation combines two sub-explanations. In the first, you are wrong about whether assassinating the leader would produce good consequences - you think it would, but actually it would produce instability, tyranny, etc. In the second, you're right - maybe you're a brilliant forecaster who can see that this particular assassination would end with an orderly succession by a superior ruler. But you know that there are far more people who think they are such brilliant forecasters than who actually are, and you either use the Outside View to suspect that you are also deceiving yourself, or at least realize that the only stable bright-line equilibrium is for everyone - true brilliant forecasters and wannabes alike - to refuse to act upon their apparent foreknowledge.

"Don't kill people" is a gimme. What other deontological bars constrain our actions?

https://www.astralcodexten.com/p/what-deontological-bars