I'm not a Lawyer-type Freeper, but rather more an Engineer-type Freeper.
I believe that there is such a thing as a "Certified Public Engineer" or possibly it's "Certified Professional Engineer". Such people have taken a qualifying examination by a state board and have been licensed to perform certain engineering functions.
Most such functions involve assuring that the public safety is maintained. One example I recall was the need to have a pressure vessel certified by such an engineer. Probably some combination of pressure and volume of a pressure vessel triggers a legal requirement to have the vessel certified. Such vessels, which include boilers, have a potential for blowing up if not constructed properly.
The term "engineer", however, is liberally applied to anyone who has an engineering bachelors degree from an accredited university.
Within specific companies, there are job titles which include the word "engineer". The minimum qualifications for such a position ALMOST always is an engineering bachelors degree, usually in a specific area.
I have seen a case of a specific job classification entitled "Engineer". This was the first rung of a ladder leading to higher levels which depended upon minimum applicable experience and demonstrated skills and abilities.
Years ago, and perhaps still, Stanford University offered a degree called "Engineer". This was between a Masters degree in an engineering field and a Doctorate in engineering.
It is definitely the fact that the word "engineer" is used frequently for many purposes which would in no way imply state certification. Even claiming to be a certified engineer would probably not lead to trouble unless one actually attempted to "certify" something. THAT would be a severe problem. The person seeking the certification would have needed to check the credentials of the certifier.