What is the legal loophole they use? In my country I can always buy Bitcoin instantly through Bitcoinic.nl (for Belgium and Netherlands), paying with my mobile banking app.
Aside from that I've used Virwox quite a lot in the past for buying Bitcoin with Paypal or Paysafecard, but their fees are just too high to make frequent use of it, like you probably know already :p
They also need to verify your account for 48 hours or so when first buying Bitcoin with Paypal, if I remember correctly. So not instant the first time
in the USA, in order to process direct exchange of fiat to crypto or the other way, you need a MSB license. it is a limited banking license and while it costs very little, will require the business to demonstrate their ability to perform this function safely and security, blah, blah... that license alone covers the entire country, BUT, you must also become legal in each state. very few states are tyrants about it, but there will be fees and more hoops to jump through. finally, before starting there is a strict information gathering protocol and information protection protocol, governed by two sets of laws. you simply cannot operate in the USA and change btc to USD or back again and provide anonymous service legally, your clients will have to, at minimum, supply proof of their identity. your store and keep these records and have to release them to the courts if asked.
virwox is not USA based but can operate through the USA because of the "middle man currency" of SLL. this cannot be done with just any alt coin or other token. Lindens came before bitcoin and it has a value. so, you are buying something using one currency, something of value, and selling it for another currency, not an exchange, but the purchase and sale of a known valued commerce item. the exchange differ in that other alt coins are not considered items, but live somewhere between a commodity and a currency. exchanging ANY alt coin for fiat requires everything i just said above, at least in the USA and for other country based companies that wish to do business with USA citizens