If the property would have been permitted at that time you will not have to bring it up to today's scode, it would be grandfathered. But, if you want to get a permit today, you will most probably have to comply with today's standards, as the inspecion will be done following today's standards.
That issue should have been disclosed to you when you bought the house, as you need to disclose it when you sell the house. And yes, in many cases it is a deterrent.
That's a different situation than Terry seems to be addressing. Building codes change all the time, so if an addition was built in 1973 that, at the time, received all necessary permits, then usually it's considered in compliance, even if the code has changed, and what was done back then wouldn't be up to today's standards. So, Terry's right regarding construction that at the time had the necessary permits. But, from your question, you're saying it never received those permits.
That's something someone familar with Phoenix regulations would have to answer.
Who is asking to have it brought to code & why?