Holiday in the US - UK resident but previous overstayer

Sorry if that title was confusing, I couldn't think how to detail it!

I am British, my husband is South African. Long story short, he's a Permanent Resident (via the EEA route) as of October last year. He's fully employed here in the UK (we both are).

We're planning/hoping to visit the States next year for a friend's wedding - my husband overstayed his first British Visa (i think it was a working holiday one at the time although they no longer exist). I think this would have been about 9 years ago if memory serves me right. He left of his own accord but it was picked up as he was leaving so there is record of it. He has since been granted PR but would this have any affect on us visiting the US? Would he be refused a visa? Presumably he would need to apply for a visa to visit anyway?

Just trying to anticipate any potential issues....

thanks!

He should mention it in the form if there is a question and yes, he needs to apply for a visa quite a bit before you plan to travel. For example, when I enquired a couple of years ago to get a visa on my South African passport, I was told to apply 3 months in advance due to strict checks.