This is a message board trope in legal discussions. Either the law matters or the whole discussion is pointless; it's not a 100 mile zone, then, but a 1650 mile zone, because, after all, nobody is following the law anyways. That might even be the case! But if it is, we're not discussing anything meaningful here.

What is plainly the case is that many people believe that the law dictates that CBP can warrantlessly search citizens anywhere within 100 miles of the border (that border including the shores of all the Great Lakes). The law does not say that, the Supreme Court has repeatedly said that CBP can't do that, and people should stop repeating the claim that they can, because that claim empowers the CBP, which is already prone to abusing its authority.

But the bogus claim is head-turning, and presumably generates a lot of money for ACLU, because it's alarming and wrong-seeming (well, wrong, period, but...).