As long as it's not illegal and as long as it isn't hurting anyone, why ban it. At first it sounds so stupid to sell air to people but if it's not hurting anyone in any way then no one should label it as "illegal". It's like selling rocks, it's stupid, but its not illegal in any way.
What is the difference between selling air and selling bottled water or other resources. Some countries need it. Who are we to deny their supplywhen a country is so polluted that its people need to wear dust masks (im looking at you china). Look at california, it is in a period of drought and they buy bottled water from some companies and they are fine