Ones where there is clear evidence that they have a good chance of achieving what they are intended to achieve, and where there is monitoring to demonstrate whether or not that is the case.
What is the whole muzzle thing supposed to achieve exactly? A vague idea of reducing the number of cases a bit, but to what end? It'll only prolong the situation even more (if it works at all, which it may well not). Despite the evidence being weak, there seems to be no system in place to monitor whether it actually makes any difference at all.
There are those who demand restrictions until there's a vaccine, which may or may not ever appear. Recent research just published seems to suggest that immunity when someone has recovered may only last a few months, in which case a vaccine is only likely to work for a similar amount of time. So what if that proves to be true? Paranoid, ineffective restrictions forever to combat the Deadly Killer Virus, even if those restrictions actually make little or no difference to spread, but cause major social issues?