My bulletin board/forum is spam-bot secure. Why? Video captcha of animated
Have fun making a bot with knowledge of every manga/anime ever made with enough horsepower to OCR everything.
Every gif file has a name, filesize, hash, etc... and with a few bucks and the Mechanical Turk, I bet they can map one of these unique identifiers to the answers to your captcha, and hello spam city! I'm guessing you're really experiencing security through obscurity, which isn't real security.
I'm pretty sure the constitution doesn't limit what government can legislate, except for the pretty specific clauses ensuring specific kinds of fundamental individual freedoms such as freedom of speech, association, freedom from arbitrary incarceration, and several other specific limitations on the government's scope of power.
In other respects, it's allowed to be a government and legislate whatever its democratically elected legislators vote to legislate.
Try reading the Constitution before taking wild guesses what it does and doesn't say. They are called "enumerated powers" and are found in Article 1, Section 8 of the Constitution.