Well...to be completely fair, the decision was based on the STATE constitution, which apparently the law suit revolved around. Not the federal constitution.
Article I, Bill of Rights, Secion 27:
Section 27. Right to bear arms; military subordinate to civil power. The people shall have the right to bear arms for the defence [sic] of themselves, and the State, but the Military shall be kept in strict subordination to the civil power[.]
www.oregonlegislature.gov
Note the verbiage is not the same as that of the federal Constitution:
Second Amendment
A well-regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed.
The Bill of Rights is a founding documents written by James Madison. It makes up the first ten amendments to the Constitution including freedom of speech and due process.
billofrightsinstitute.org
Like it or not, the Oregon does not contain verbiage which says anything on the order of "shall not be infringed", from which we derive the limitations which are placed on the federal government.
Rather, it simply says the people shall have the right to bear arms, and for defense of themselves and the state. The caveat included is that the military shall be kept in strict subordination to the civil power...which, in context to bearing arms in the same sentence, implies if those arms are used in defense of the state.
There's nothing whatsoever in there which says the state cannot impose other conditions, restrictions, or limitations. "Infringements", as we like to call them with respect to the Second Amendment RKBA.
HOWEVER...this is a double edged sword. The simple statement "the people SHALL have the right to bear arms for the defense of themselves" could potentially be interpreted in the courts as including felons. That would be an interesting battle, properly fought and with the right people being defended in court. For example, people convicted of non-violent felonies who are denied their RKBA. Why should they be denied this right?