With all due respect and food for thought for those interested regarding cat-bypass modifications; here is a link to the Federal Law:
http://www.epa.gov/air/caa/title2.html
The Federal Law takes precedence over any state law regarding vehicle components related to Federal EPA standards of the Clean Air Act.
Some may even find it interesting to note there is not a reference to "off-road-use" being an exemption to the law. While some products are sold under this guise, it does not protect the end-user from violating the law.
You will find the law very restrictive with regard to any modification of any kind to
any vehicle component by anyone -- ever.
Reading the sections of "Actions to Restrain..." and "Civil Penalties"; you will see the law's legal reach is quite deep, restricting virtually anyone from making modifications.
While I agree with most; enforcing the Act has not made headline news, and I have never known there to be an "enforcement task force" running around the country arresting people; I would pause and be sure to read the law so you have an understanding of it before moving forward on any modification related to components required to exist by Federal Law.
Here are a couple sections of the law...
42 U.S. Code § 7522 - Prohibited acts (3):
(3)
(A) for any person to remove or render inoperative any device or element of design installed on or in a motor vehicle or motor vehicle engine in compliance with regulations under this subchapter prior to its sale and delivery to the ultimate purchaser, or for any person knowingly to remove or render inoperative any such device or element of design after such sale and delivery to the ultimate purchaser; or
(B) for any person to manufacture or sell, or offer to sell, or install, any part or component intended for use with, or as part of, any motor vehicle or motor vehicle engine, where a principal effect of the part or component is to bypass, defeat, or render inoperative any device or element of design installed on or in a motor vehicle or motor vehicle engine in compliance with regulations under this subchapter, and where the person knows or should know that such part or component is being offered for sale or installed for such use or put to such use.
Everyone should note; the fines for mechanics, car dealers, marketers of by-pass products and such are the highest.
Their fine is up to $25,000 per part, not per incident. In other words, two parts replaced could fetch a fine of $50,000. Where the fine for individuals is far less.
Again, I do not know of anyone who has been arrested and charged yet, so I am not losing sleep over it yet; but you can bet someday there are going to be some people the government are going to make examples of. It has happened in the last couple years to Vance & Hines for their avoidance of the laws.