All police officers in Alaska swear to enforce BOTH state and Federal law. Further, the nominal principle of US law is that Federal law TRUMPS state law.  There are many Federal crimes which are not state crimes - but they don't disappear because a state has no such rule.  It is on this basis that the Supreme Court has invalidated Alaska's Constitution re gay marriage - in spite of NO Federal statute legalizing it.  Precisely why we have inconsistent application of the principle of Federal law is superior is unclear.  Most of all to those on the front line, sworn to uphold both.  Have a little sympathy for them.