Depends on the model... "commercial grade" rifle scopes are exempt from ITAR controls and can be sent to countries listed as "friendly" (see the US Customs list) provided the customs paperwork is filled out correctly. I believe you need to reference ECCN 0A987 for specific details on rifle scopes and what can and cannot be exported.
"Military Grade" rifle scopes are ITAR-controlled and would require an export permit and associated paperwork in addition to going to a country listed as "friendly."
If it's a commercial-grade scope and the recipient is in a "friendly"-classified country you can state "Commercial Grade Riflescope - No Export License Required Per ECCN 0A987" on the customs paperwork and you should not have an issue.
Unfortunately the definition between "commercial grade" and "military grade" in regards to a rifle scope is somewhat gray and open to interpretation... I certainly wouldn't attempt to send *any* scope that is/has been issued a NSN out of the country. Being that you're selling an S&B, I specifically wouldn't try to ship any PMII model out of the country. An Exos, Stratos, Zenith, Summit, or Klassik hunting model maybe-- but I wouldn't even attempt a PMII. Because of the somewhat vague definitions of what makes up a "military grade" scope vs. a "commercial grade" scope I've heard of scopes with ranging and/or illuminated reticles being held up in customs because whomever inspected the scope decided to classify them as "military grade" because of those features.
I've sent several commercial-grade scopes to Australia (a listed "friendly" country) and each time I was biting my nails until they were in the hands of the buyer even though I followed all applicable regulations and correctly filled out the customs paperwork. Until the tracking number showed "delivered" and I got an email from the buyer saying he had the scope in-hand I was waiting for a phone call or visit from Customs. Never got one but I was still nervous!
Additionally, I vaguely recall from doing my research on the Customs website that Canada didn't sign and/or opted out of some ITAR related agreement with the US several years ago and thus may not be on the "friendly" countries list for receiving a rifle scope. You need to do *thorough* research before printing a shipping label & customs form to keep yourself out of potential trouble.
If you have even the slightest doubt or have even the slightest reservation about sending the shipment... don't do it. The potential hassle and/or legal issues aren't worth it!