If you register to vote in a federal election, you'd need to show a document proving you're a U.S. citizen — like a passport or a REAL ID-compliant license/ID that specifically shows citizenship status — before your registration could be accepted; simply signing a form and swearing you're a citizen, which is how it often works now, would no longer be enough. States would also have to set up a backup process for people who don't have those documents to prove citizenship another way, and would be required to actively check voter rolls and remove anyone found to be a noncitizen. Election officials who register someone without the required proof could face lawsuits or criminal charges under the bill.