Indeed; whether that's 'signing away' sovereignty is a different matter;
like membership of the EU, a key aspect of sovereignty *is* the ability for a country to make long-term agreements... many of which are useful (or even vital) to a country's national interests.
The Q. of Bilateral Investment Treaties is more about the ability of a state's diplomats to negotiate a favourable treaty (or not)... that said BITs are notorious for foregrounding private sector interests....