If you get a chance, look up the state question—actually it does ban others by way of stating “or any other foreign” laws, or similar words. It does point out Sharia, but not exclusively.
https://www.sos.ok.gov/documents/questions/755.pdf
First off, the ban against the use of international law wouldn’t cover religious law. International law is the formal creation of states and treaties, not religious groups.
Now after the proposal singles out Sharia law in particular, the next sentence states “The courts shall not look to the legal precepts of other nations or cultures.” For nations, that’s straightforward enough.
But if that’s meant to encompass other religious law besides Sharia, then at the very least you’ve got a serious problem with vagueness. What qualifies as “other” cultures? Is Jewish or Old Testament law “other”? Is papal law? (For that matter, Roman law? English common law? Native American tribal law? That last one could be a big problem for courts in Oklahoma, in judging Indian disputes.)
And if not all religions are deemed “other,” then the consequence of that is that Oklahoma has created a law that respects a particular establishment of religion. Namely, whatever establishment they have not formally deemed to be an “other” religion.