This is the best argument I've read yet as to why BOI reporting is unconstitutional.
Essentially, the government is claiming they can force you to report your ownership information just because your business might engage in interstate commerce someday. But that's like saying they can regulate your newborn because the kid might grow up to be a truck driver.
The Commerce Clause doesn't work that way. You can't regulate the mere existence of a business based on what it might do in the future. Filing incorporation paperwork isn't an "economic activity" - it's just paperwork.
This argument was made by Sheng Li on behalf of the New Civil Liberties Alliance in their amicus brief:
According to the government, Congress may regulate the creation and continued existence of corporate persons based on the theory that such entities will one day engage in economic activities that impact interstate commerce. This court should deny the stay request because it is based on a boundless interpretation of the Commerce Clause that is utterly incompatible with limited government.
Such mere filing is not an economic activity regulable under the Commerce Clause, because it does not involve the production, consumption or exchange of any good or service for which there is a national market. Nor can the government anticipate future economic activity that a corporate person will one day engage in to justify regulating its birth and continued existence under the Commerce Clause.