K1 visa and I-485

[British45 1]

So at my medical for my K1 visa i admitted to past marijuana use. I know that this can result in a 1 year ban and then approval of the K1 visa after the year is up. My question is once the Visa is obtained and you file for AOS via I-485 and the questions arises about past drug use. Now they will know from my medical results that i had used it in the past but do not currently use it, so there for the only thing to do will to be answer yes to this question. Could this still result in me being inadmissible even though i was approved for my K1 by a CO in London once i go for the green card interview? 

[Lil bear 3,831]

Moved to AOS  from K1 visa as the question relates to AOS process 

[payxibka 10,044]

Which exact question are you worried about?

[British45 1]

Part 8 question 30

 

Have you EVER violated( or attempted or conspired to violate) any controlled substance law or regulation of a state the United States or foreign country?

[British45 1]

From what I've been researching there is no controlled substance law that states having used marijuana violates the controlled substance act. On top of this for me to be answer yes to this question it would require me to know what controlled substance law I could have possibly violated. Plus if I was approved by Consolur Officer in London then that means there was no finding of violation of a controlled substance law, because if there was then I would be deemed inadmissable then and there on criminal grounds. So I should be able to answer no to this question, can anyone give more light on this? Or does what I have said sound correct