In Washington State (and most, if not all other states)
Any homeowner with the proper permit(s) can perform work on their home - but the work is required to be done to the applicable code, inspected and signed off, just like a professional contractor. Just because you're DIY doesn't mean you get a break from being code compliant.
So when you pull a permit, the work you do is required to be compliant to the spec at the time. e.g. electrical work permitted today is generally bound to the 2008 National Electric Code (aka NFPA 70). Work I did on my house in 1999 is compliant to the 1999 NEC, but if my permit says I went and made alterations to that work done 10+ years ago, I would still have to make any upgrades to meet the 2008 spec.
The difficult part is knowing what or who is the governing authority or specification regarding the work you're doing. Calling your county/city building inspector should get you the right answers when there are situations where different code bodies offer ambiguous or conflicting information.
Also just visiting the website for your city/county code enforcement office (mine does this) will have guidance on what work requires permitting and what doesn't require a permit.