[OneWingedShark]

>I would agree that a county cannot pass a law to overrule state law.

The question immediately becomes: is the state law valid.
If the state law is contrary to the Constitution of IL, then the law is void. (See the opinion of Maybury v. Madison.)

[Enterprise]

I wish the people of Pike County well, and I hope they have the stomach, and the finances, for the coming legal fight. The State of Illinois is going to quickly step in and have a hack State Judge rule against the people. Then they have to appeal it to a State Appeals Court, and will probably lose, and then they will have to appeal it to the State Supreme Court, where they will probably lose again.

If the people claim a federal right, a hack federal judge in Illinois will rule against them. Then they have to appeal to the Federal Appeals Court in their district, where they will lose again. And then they have to appeal to the USSC, and the Court may or may not hear the appeal, and if they hear the appeal, there is no guarantee they will side with the people. I make no predictions on the chances that the people of Pike County might ultimately prevail.

And there are other issues that the people might consider, like the right of nullification at trial should the state begin arresting citizens of Pike County for violating State Laws. But if one of the citizens somehow gets arrested for a Federal Statute, then the trial can be held outside of Pike County where the chances of jury nullification might be very small.

The varied scenarios that this discussion can take could keep us both busy for years.

[TXnMA]

"The question immediately becomes: is the state law valid."

IANAL, but it would seem that a challenge of a State law by a county with a 5.8:1 mandate from its citizens would be a much stronger case than (for example) a NRA-supported lawsuit by an individual.