Green Card / Criminal Record / Waiver

I am from the UK, also a Canadian citizen (PR since 2011) and I have met as US citizen. We wish to marry and live in the US but I have a criminal record from the UK. It was for posession with intent to supply a controlled substance (cannabis - 8 grams).

The record is from when I was 21 and I am now 45. I know that this is BAD and under normal circumstances is grounds for inadmissability. My potential spouse is a caregiver for her father however and as far as I understand the process there is a chance that we could apply for a waiver of inadmissability for this reason.

Would I be correct in thinking that or is my crime not open to the waiver system?

Have you had any other issues? If not use an immigration attorney with a successful track record of waiver approvals who will focus on your one time issue, its age and the amount of product. You were 21 thus an adult. Your sponsor being the caretaker of a family member has no bearing on your immigration.