Pardons Canada: Denied entry to the US for a pot offence in 1986

Visitor: I had travelled through the US many times via land and air until approx 2008 when I was crossing the border into the US  the border services pulled my passport and accused me of having a criminal record and quoted an alleged incident in 1986 when I was charged with possession of marijuana.
I have since had my fingerprints done (maybe 5 yrs ago) and then sent them off to Ottawa and received a notice of “no criminal activity recorded”.  I was in contact with the North Vancouver RCMP who also confirmed that there is no record of any arrest or incident under my name.
I returned to the US border to submit the documents but they insisted that I apply for a US Entry waiver which costs $575 US to approve which implies that I am guilty of an offense.  As that evidence does not exist I am not sure what the best way forward is to gain access to the US.

Pardons Canada: You will need a US Entry Waiver or I-192 to have access to the US since you have already been denied entry. The only way to get accepted by the Americans is to complete the application for a US waiver. The longest a waiver is good for is five years and then you will need to re-apply. There is no getting around this once you have been entered into the US system, even though your offence was over 4 decades ago for a small amount of pot.

Pardons Canada undertakes all necessary steps and procedures for removing your criminal record, including: Pardons/Record Suspensions, Purges, Photograph & Fingerprint Destruction, and U.S. Entry Waivers.