technically tint shops are breaking the law, but any tint shop that refused to do illegal tints wouldn't be a tint shop for long, & no government agencies are really cracking down on them either because stopping the source would be a huge revenue loss for them, so it's business as usual. if they REALLY wanted to stop illegal tint they'd crack down on the source, but I think they'd rather just earn huge $$$ from all the citations they can get from this.
when they decided they wanted to really stop minors from buying cigarettes they knew just how to do that. many businesses lost there licenses & now it is widely known that there just not playing around, so now a minor can't just walk into any store & buy cigarettes or alcohol for that matter, they could do the same with tint & make it that no tint shop would dare putting illegal tint on a strangers car for fear of loosing there license to do business if they really wanted too
what about tuners? even the big dogs... the majority of what they do is illegal too, not only illegal but even on the federal level. all the turbo's & SC's, all the emissions tampering & alterations... just knowingly doing this on a vehicle that will be operated on the road is illegal. of course your invoice will say very clearly that any mods they perform for you "may not be legal on public roadways & is provided for off road use only" so they are somewhat covered by this loophole technicality & again, no real heat is coming down on them either, but a big part of there business is illegal "technically" with the exception of the very few CARB legal kits...