If the legislature were to write an untrue "fact" into law, such as "black is white" or "all oranges are blue", how would the judiciary deal with it?
I'm particularly interested in examples in English and Welsh case law as to how the courts have dealt with such a scenario, but this may be new territory in England and Wales and perhaps there are international examples of the approach taken by the courts.
There was a recent case in the US state of California (Almond Alliance v. California Fish & Game Commission) that got a lot of press because the court found that bees were fish. The California Endangered Species Act allows the state to protect any "bird, mammal, fish, amphibian, reptile, or plant" but defines "fish" as "a wild fish, mollusk, crustacean, invertebrate, amphibian, or part, spawn, or ovum of any of those animals." The court ruled that bees were invertebrates so, under this particular law and definition, bees were fish and thus eligible for protection.
Realistically, the court would apply the same logic here. If the legislature passed a law which included a definition that "white" was "any hue-less color such as white, grey, or black" then that is the definition that the court would use when interpreting that law. If the law said that it was illegal to "paint a mailbox white", the court would simply find that "white" uses the definition the legislature specifically adopted rather than the colloquial definition. Thus the law banned mailboxes that were white, grey, or black.
Statutes do not define words in a vaccuum. Or if they do, there just is no effect. Statutes define words for particular purposes in particular contexts.
Statutory definitions are also used to expand the usual scope of a word or expression, for example:
In this section,
"fish" includes shell fish, crustaceans, and marine mammals;
...
In these examples, the statutory definition enlarges the ordinary (or technical) meaning of the defined terms by including things that might normally be thought to fall outside their denotation.
(Ruth Sullivan, Statutory Interpretation, 3rd ed. (2016), p. 81)
If being "blue" had a particular significance in a statutory scheme, and a statute deemed all oranges to be blue, then for the purpose of that statutory scheme, oranges would be treated as other blue things.
