This summary is not the rule. The rule text controls.
If your case involves a law from another country, you need to tell the other side and the court about it ahead of time. You can do this in your written court papers or through some other clear written notice. The point is to avoid surprises, so everyone has a chance to prepare.
When the judge needs to figure out what that foreign law actually says, the judge isn't limited to the usual evidence rules. The judge can look at almost any helpful source, including expert testimony, articles, or other materials, even if that information wouldn't normally be allowed under Hawaii's evidence rules. This gives the court more flexibility to get foreign law right, since it can be hard to prove in a normal courtroom setting.
Finally, once the judge decides what the foreign law means, that decision counts as a ruling on a legal question, not a factual one. This matters because it affects how the decision can be reviewed later if someone appeals. It also means the judge, not a jury, is the one who decides what the foreign law says.