Look up concepts such as "first-sale doctrine" and "exhaustion of rights". Basically, once AquaLung has legitimately sold an item to anyone, they have no more right to say what becomes of it. If they sell 30 regulator sets wholesale to an LDS, and that LDS liquidates and sells its remaining stock to LP, LP is free to sell it. There is nothing AL can do about it, as their rights ended once they sold it to the original LDS. They can choose never to sell through that LDS again, of course, but that's between AL and their retailer and has nothing to do with LP, since LP does not *have* an agreement with AL.
If LP goes to Europe and buys 100 dive computers, they have every right to do with those computers what they want, even if that is selling them in the US, where the manufacturer will not support the computers. The manufacturer has no right to prevent the resale. The only way the manufacturer would have a right is if LP had a contractual obligation, which they would not have as they have not elected to become an authorized reseller.
This only becomes a grey area (pun intended) when you swap *licensing* for *sale*, such as in software. That, however, is a far more complicated topic that is *well* outside the scope of a thread on ScubaBoard. (There are plenty of cases actively being litigated on that front, so feel free to enter law school to get on that train.
![Big Grin :D :D](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
) Thankfully, scuba equipment is *sold*, not licensed, so that's all irrelevant.