You gotta realize that Federal Reserve Notes (FRNs) are a PRIVATE scrip, just like casino tokens. And just as casino tokens are legal tender everywhere within the casino, FRNs are legal tender everywhere within federal jurisdiction.
They're NOT money, just as casino tokens aren't money. Just a money SUBSTITUTE issued by a PRIVATE party, as the federal gov't is a FOREIGN corporation in respect to states of the Union. But it so happens that 14th Am. US citizens are subject to federal jurisdiction, WHEREVER they are in the world, so they must abide by the US/casino rules, under which the tokens are means of payment.
And just as you can't use REAL money to gamble in a casino, you can't use REAL money (silver and gold) within jurisdiction of the federal US. And that's because both of these are under PRIVATE rules (Public POLICY), while in the REAL world, Public LAW applies. Well you CAN use real money in US, but the US "gov't" won't accept them, because then they'd have to deal with you under common law, where their private, corporate nature would be revealed.
So basically, when you pay with REAL gold money in United States, you're entitled to protection of Public LAW, and are NOT subject to its PRIVATE rules (Public POLICY).
And the reason why States can enforce their arbitrary rules on you, is because when you use FRNs as money, you're using NEGOTIABLE INSTRUMENTS, which is COMMERCE, and States have authority to regulate commerce.BUT when you make private contracts in real GOLD money, then you no longer engage in commerce, and so are entitled to protection of Public (common) LAW, and no longer are under State's statutory jurisdiction.
So buying something with gold in US, would be like buying something with FRNs in a casino. Such a transaction in a casino would NOT be subject to casino rules, as it was not done with casino tokens, but with real money, which requires real law, not a private one, if there's a dispute. Ergo, transacting in gold money, entitles you to protection of real law, and is outside of statutory jurisdiction of the State. You just gotta demand it.