> A building code change that requires old buildings to be brought up to current code would not run afoul of the prohibition on ex post facto laws as long as an

> A building code change that requires old buildings to be brought up to current code would not run afoul of the prohibition on ex post facto laws as long as any penalties for not complying only apply to non-compliance that occurs after the law is enacted. My personal experience having owned multiple properties is that code changes rarely, if ever work the way you are describing. I've actually renovated a few kitchens, and had to deal with GFCI because the law around the permit for construction required us to, not because the code change was applied to pre-existing non-GFCI outlets. It would be impossible to maintain a property if the law worked as you described - the government could declare the kind of shingles on your roof illegal, and take your property for non-compliance, which is exactly why ex post facto laws are unconstitutional.