To meet both federal and state requirements, at ShipYourReptiles we recommend users mark each box with "Wildlife- Live Harmless Reptiles".
They should then have an itemized invoice or packing list with scientific names and quantities immediately available, which we suggest as immediately under the top flap.
Fish & Wildlife inspectors do NOT want to actually have to go into the box (past the insulation) to ascertain the contents.
There was a reptile dealer prosecuted on Lacey Act issues in 2014 or 2015. It wasn't over a single shipment issue, but over a larger and repetitive issue, also involving prohibited species. I don't remember the particulars.
We see packages audited and inspected regularly when they are going into California and Florida. When shipping to either of those states, you should EXPECT that your package will be inspected.
If the package is inspected but not properly labeled, it may be returned to you, or it may be delivered, but you will hear about it through a fairly nasty letter and a threat of $10k+ fines if you do not comply in the future.
I have never heard of someone prosecuted over single package labeling, but there is effort on package auditing and inspection, so we do encourage users to comply with the labeling requirement.
We address Lacey Act labeling a few times on the ShipYourReptiles site.