How do we accomplish that goal of not making treaties that favor multi-nationals?
Allow US manufacturers to compete on a level field for US and foreign consumers. Right now many overseas companies do not have to comply with the same level of overhead burden of regulations for child labor, safety, environment, taxes, licensing, etc that US companies do. Heck yes, China and Mexico can produce goods cheaper because they pay much less to the worker and government, and they have much less red tape. It is a wonder we have any US manufacturers left.
My understanding is that libertarian ideology is not meant to drive a one-world community. It intends for the interaction of competing entities: individuals, companies and importantly, nations. A nation should have few internal regulations and taxes and get most of its revenue from imports. We are nearly upside down on this now in the US. We should make it so that if you want to compete in the US, then you have to manufacturer in the US or pay high import duties on everything.
* Greatly reduce the regulations burdening US companies (this is a test of your libertarian souls

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* Significantly raise import taxes
country by country (not same across globe or region) to counter real life imbalance of using prison labor, child labor, lack of regulations, govt subsidy, etc. This has to be totally disentangled from political and military strategy and favors.
* Make trade treaties that also give US companies equal access to trade partner's consumers. This is less important because the US is the the golden calf of consumerism. Therefore, our focus should be more about leveling the field for our manufacturers. Currently "free trade" treaties are more about giving unfettered access to consumers and not much about making manufacturing field level.