In the softwood lumber dispute that's been going on for decades, the US raised (legitimately) the point that in Canada, land is granted by permit to loggers for only nominal fees; in the U.S. loggers have to pay significant amounts for rights to log. This is effectively a gov't subsidy to Canadian loggers by comparison with American loggers, allowing Canadian loggers to sell softwoods at a lower price.

This is the difficulty with discussing "trade barriers": things that are simply handled differently in different countries can be (arguably) economic factors that discriminate against one side or the other, hence they're trade barriers. Complicating it further, one can create barriers that have plausible deniability, or point to unrelated factors and scream "TRADE BARRIER".

I know someone who was involved for a while in the softwood lumber discussions. Just an absolute snake pit trying to suss out what are real barriers, intended barriers, relevant inputs... and all of this in the context of negotiations over the same, so everything is also "does he mean this or is he distracting us from something else or just building up a talking point to surrender later?"