22 were used for assignation pistols only because of the ability to very effectively silence them.
They can be effectively silenced because they are so low power, lower speed bullet.
You can kill with them. But because they are such low power, it is typical for states to ban hunting with them.
.22s are allowed for hunting in almost every state. The restrictions are on deer and bear in VA. Has to be .23 or larger.
Many states also ban hunting deer with a .223 mil-round rifle with the big cartridge shown in post #4.