Concerning the less then an ounce rule... that seems to be statutory (written in AK's laws) so you can rely on that. However it seems to be limited to "in your own home". I'm not sure about in a car, etc.

The less then 25 plants rule seems to be from a ruling of the Supreme Court in a case. That being said, with some different Justices the next Court could overrule that decision. So that is less reliable then the statutory law, but still seems pretty reliable since it was the Supreme Court.

As far as Federal Law... the Feds (DEA, etc.) can bust anyone in the country, in any state, at any time, for violation of Federal Marijuana laws. The Supreme Court of the United States has held that Federal Drug Laws overrule State Drug Laws. That is how the DEA gets away with busting cannabis dispensaries in California that are legal according to State law.