As of January 1, 2006, Texas will only grant PE exam waivers to people who hold PhDs and have 4-6 years of creditable experience, and to people who are licensed in other jurisdictions who have 12 years of creditable experience. In addition, they have to have their application in by the end of this year. Everyone else (and everyone who applies starting in Jan.) MUST take, or have taken, the PE exam. I'm glad to see we're getting serious.
As for State vs. Federal, the 10th Amendment reads: "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." That says that States get to set their own rules. Article IV, as I read it, says that CA, for example, must honor rulings in TX--e.g., CA cannot protect a fugitive found guilty in TX even if the particular crime is not illegal in CA. I'm not a Constitutional scholar, by any stretch, but when you apply Art. IV to licenses, you delve into a whole host of issues, material for a different forum.
On a separate, but related, note: what seal is required for Federal work, like on military installations?