Dennis Hastert was 6 years old when the current version of the law making it illegal to lie to the FBI was created. It's origin goes back to the False Claims Act of 1863, long before the FBI existed.
His big issue, as was Martha Stewart's and a bunch of other folks, was lying about it.
The secondary issue of reporting financial transactions is based on a law from 1970, the Bank Secrecy Act. The requirement of the bank to report suspicious activity was part of the Annunzio-Wylie Anti-Money Laundering Act from 1992.
While it might be nice to claim that Hastert was hoisted by his own petard with the Patriot Act, the fact is the Patriot Act's expansion of these previously existing money laundering and bank secrecy acts were related, primarily, to international money transfers. In fact, the title of that section is, "International Money Laundering Abatement and Financial Anti-Terrorism Act of 2001."
Although the Patriot Act expanded the reporting requirements of a structured transaction, the banks were already required to report such structured transactions to the Financial Crimes Enforcement Network by the 1992 law as part of a Suspicious Activity Report. The IRS already had authority to seize monies given a warrant based on Suspicious Activity Reports.
The big changes found in the Patriot Act were related to making it easier to recognize structured transactions, the expansion of the definition of a financial institution and a number of changes to the infrastructure and reporting mechanisms related to the reporting requirements.
What Hastert did was illegal long before the Patriot Act.
(There is a section of Wikipedia that claims that the Patriot Act made it illegal to to structure transactions in a manner that evades reporting requirements. However, that was already illegal and the wording in Wikipedia is more probably related to the structuring of foreign transactions or transactions that involve foreign currency and coin.)
I won't defend either Hastert or the Patriot Act - they both suck. But the fact is, these reporting requirements go back a long way and they sucked just as much before 2001 as they do now. This case is another example of why you don't answer the FBI's questions about anything without an attorney.