The Lacey Act
Updated
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The first prohibition
It is unlawful for any person to import, export, transport, sell, receive, acquire or purchase any fish or wildlife or plant taken, possessed, transported or sold in violation of any law, treaty or regulation of the United States or in violation of any Indian tribal law.
The second one adds states and foreign countries
The same acts, in interstate or foreign commerce, for fish or wildlife taken, possessed, transported or sold in violation of any State law or any foreign law. So a state collecting regulation becomes a federal matter once the specimen crosses a line.
Plants are included, with their own conditions
Plants taken in violation of a State or foreign law protecting plants, regulating theft, taking from a park, forest reserve or officially protected area, or taking without required authorization, and plants taken without payment of required royalties or fees.
Which reaches pressed botanicals and herbarium sheets
Collecting from a national or state park without authorization is exactly the kind of taking paragraph (a)(2)(B) describes. For a herbarium the collecting permission is part of the specimen record, not an administrative extra.
Acquire and receive are in the list
You do not have to be the collector. Buying or being given a specimen that was unlawfully taken is itself named, which is why provenance matters to a buyer as much as to a collector.
So provenance is the control
Where, when, by whom, under what permission. Without it a specimen cannot be moved or sold with any confidence, and with it almost every question in this section answers itself.
And it is cumulative with the other statutes
The MBTA, the Endangered Species Act and state law all continue to apply on their own terms. The Lacey Act sits on top, which is why clearing one of them is not clearing the question.