That's actually messed up, IMO.

That paragraph does appear under the "definitions" subtitle of the code, which means they're defining the term, which is not necessary a restriction on its use.

There are penalties for claiming to be a "registered professional engineer":

672.310     Investigation of identity of person claiming to be registered

But then you get to this, which is really messed up and overbroad, IMO:

 672.007 Acts constituting practice of engineering, land surveying or photogrammetric mapping. For purposes of ORS 672.002 to 672.325:
      (1) A person is practicing or offering to practice engineering if the person:
      (a) By verbal claim, sign, advertisement, letterhead, card or in any other way implies that the person is or purports to be a registered professional engineer;
      (b) Through the use of some other title implies that the person is an engineer or a registered professional engineer; or
      (c) Purports to be able to perform, or who does perform, any service or work that is defined by ORS 672.005 as the practice of engineering.

I would challenge that, because it seems to have an overbreadth issue, which means it can be challenged as a Section 1983 first amendment violation.