Under US law it is illegal to use localbitcoins. It’s a violation of money transmitter laws.
https://kelman.law/blog/money-transmitter-licensing-for-u-s-...
https://kelman.law/blog/money-transmitter-licensing-for-u-s-...
The same for selling bitcoins. You can do it a few times but if you make it a business you become a MSB.