The Jedi Order learned of the "Rule of Two" around 188 BBY during the Dark Jedi Conflict
OK, it's been a while since I saw TPM but I'm pretty sure that's not what Yoda says. IIRC the line is: "Always two there are. No more, no less. A master and an apprentice."
That was Yoda's line in the movie, yes. DarKush
was quoting Darth Bane's rule.
Mr. Laser Beam wrote:
Doesn't George Lucas treat the EU novels as canon? I thought SW's attitude towards such things was different from Trek.
The SW franchise approach is different from Trek, but not quite in the way you're thinking. In SW, there are varying levels of canon
- G-Canon is "George Lucas canon" - namely, the movies themselves and anything else Lucas decides is canon.
- T-Canon is "Television canon" - The Clone Wars and its feature film, and supposedly Tartakovsky's Clone Wars microseries. The live-action series, if it ever comes to fruition, would belong here. This tier apparently does not, however, include the old Ewoks tv movies or cartoons, or the Droids cartoons.
- C-Canon is "Continuity canon" - all transmedia works (books, comics, video games, etc.) that are included in the effort to maintain a consistent continuity. In other words, the modern Expanded Universe.
- S-Canon is "Secondary canon" - older works published prior to the consistent continuity efforts (Marvel's comics, for example). Some elements of these works may be moved into a higher tier when contemporary works include references.
- N-Canon is "Non-canon" - "Infinities" ("what if") tales, and other works that are explicitly deemed by Lucas and Lucasfilm to be non-canon. An obvious example would, of course, be The Star Wars Holiday Special.
See the link above for more detail and many quotes, if interested.