The idea of a "causal nexus" is not accepted in any law system (natural or positive). The fact something can happen due to your actions can't be used as an ethical argument to limit your freedom of action.

From the perspective of individual freedoms the ban of guns is unacceptable under the pretense they might end up harming others by chance; if that's the case, the police and the military themselves shouldn't have guns. Besides, populations that live under strict gun control surprisingly have more people being harmed by guns than populations that don't have strict gun controls (case in point: criminals don't care about laws, by definition).

Also under the perspective of individual freedoms, the enforcement of masks is not justifiable. If you feel unsafe due to a potential virus outbreak, take your precautions but don't force others to do whatever they want to do. Otherwise, we'd fall into authoritarianism.