Proposed but failed legislation would have required the Iowa Supreme Court have a supermajority to rule an Iowa statute unconstitutional. This legislation would have required five of the seven Iowa Supreme Court justices to agree.
Interestingly enough, the proposed bill may have been unconstitutional. It is likely that an amendment to the Iowa constitution would have to be made to implement such a change to the law.
Naturally, the Iowa Supreme Court would review any such bill, if it passed. Of course, the question would be what vote count would be required to overturn it. Thankfully, the bill did not pass.