The answer is that it is a complex, and changing topic. To try to illustrate this, we will consider her just one small part of the law; when you can defend yourself against an aggressor.
Lets begin by looking at what the relevant section of Oregon law actually says:
ORS 161.219 Limitations on use of deadly physical force in defense of a person Notwithstanding the provisions of ORS 161.209 (Use of physical force in defense of a person), a person is not justified in using deadly physical force upon another person unless the person reasonably believes that the other person is: (1) Committing or attempting to commit a felony involving the use or threatened imminent use of physical force against a person; or (2) Committing or attempting to commit a burglary in a dwelling; or (3) Using or about to use unlawful deadly physical force against a person. [1971 c.743 §23]
Seems pretty straightforward. If someone is trying to or threatening to use either physical force, or deadly force against you, you can use deadly force to defend yourself. The only real limitation is in 1) that they have to be committing or threatening to commit a felony involving that use of force. In general, any crime involving the use of (significant) force or deadly force against you is going to be a felony.
Not quite a "stand your ground" law in the style of that of Florida, but good enough (from the point of view of someone being attacked).
Note that there is absolutely nothing about having to retreat.
Charles then appealed to the Oregon Supreme Court at the beginning of 1982. The court denied his appeal. Their reasoning can only be called strange (State v. Charles 647 P.2d 897 (1982)). Basically they didn't look at the 1971 law (ORS 166.219 above), but dragged up various statements dating from well before that date as well as discussing laws in other states, and proposed laws which were never passed. Off to jail with Mr. Charles.
In addition, this created case law, in pretty much direct contradiction of the actual law, and because case law is (almost) always followed, on the basis of giving equal treatment under the law, Oregon became a "retreat" state, where you had to have absolutely no way to get away before you could defend yourself. This, without any change in the actual law.
The prosecutor decided to treat it as murder rather than self defense, based upon the CHARLES precedent, because SANDOVAL did not attempt to run away.
To make matters worse, the prosecutor insisted that the following instruction be given to the jury, and the judge agreed:
Sandoval was convicted of murder.
He appealed on the basis that the jury instruction was incorrect. His appeal was rejected. He then appealed to the Oregon Supreme Court, which, 25 years later, had a different set of judges. Their analysis (State v. Sandoval (2007)) is very interesting. Not only did they examine the actual law, as written, but of necessity examined the prior case law (Charles). They were not complimentary about the decision. Sandoval's appeal was upheld, and Oregon reverted back to its status of a (pretty much) stand your ground state. Again, with no change in the law.
The point of going over this is to illustrate that simply reading the law is not enough. Activist judges can (and do) stand the law as written on its head, and you have no way of knowing the current state unless you are skilled in legal research and can evaluate the written law through the filter(s) of one or more applicable legal precedents. Lawyers really do earn their money. People that just read out the written law to you without pointing out the hidden dangers of taking it at face value, do not.