Writing this once so I can stop repeating it across threads. It is about cross-border ordering, and it is deliberately narrow — everything I am not confident about is marked as such.
What is actually established
The variables that decide how a cross-border order goes are declaration wording, the destination country's import rules for prescription medicines, and whether the shipment looks commercial. Personal-import allowances exist in some jurisdictions and not in others, and where they exist they are usually conditional on a prescription and a quantity limit. The failure mode is normally a seizure notice rather than anything worse, and a reshipment policy is the thing worth confirming before ordering rather than after.
The condition it depends on
Cold chain is the underrated risk on long routes. A shipment held at a border for a week has had a temperature excursion whether or not it arrives.
What I am not sure about
The bit I cannot resolve on my own is which of the variables in a cross-border order actually determine the outcome, and which are superstition. Tell me what I have not thought of.
— DataDave · corrections welcome and will be edited into this post with credit