I'm not too well versed in the criminal clearance process since mine didn't come up. Question though: is your husband in Canada or is he allowed to enter Canada? Because (I think) if he is allowed in, I would say he is not inadmissible and therefore the charge shouldn't come up. BUT I can't be sure. The good thing is that since it's been over 5 years since the sentence was completed, if you need to you can apply for criminal rehabilitation. It will add a bit of wait time, but worth it if it gets him in.
And to be fair, they always tell you that just because one CBSA officer made a decision, it doesn't mean the next one can't make a completely different decision. I have flown into Canada many many times since my arrest and NEVER had it brought up. But when I drove across the border and my boyfriend was importing his car, they did a background check on me and said I was inadmissible unless I could show proof that the charges were dropped. Which I didn't have on me because I had completely forgotten about the arrest. Then the officer called me back up and said she would treat it as a juvenile offence (I was 18 when arrested) and let me go. Which sounds like a load of crap to me haha. I think she probably realized only the arrest showed up and no charge so she had to let me go.
If any senior member has more info on this, please chime in!