Yes you may take Bear Spray through Canada to Alaska however it must state it is for bear repellant vs for personal protection against a human. At least that's how it was in summer 2016 when we last went. Rules change almost as often as the wind direction for what you can't and can take into the country. One year they were confiscating any canned food products containing beef such as beef stew etc. Had to watch out for that Mad Cow disease back then.
I used to always carry a rifle when I transited between my home in Alaska and WA state. I was returning from WA over one of the boarder crossings back into Canada and was asked "any firearms"?, yes 7mm Mouser long gun behind the seat, unloaded. He made a note on a pad and gave it to me. Go to the office and visit with customs and imigration. So I did both and was told to return to my truck and wait for inspection. A young Canadian boarder agent came out and looked through the bed of my trucks contents then headed for the cab. Poked around, looked under the seat then folded the seat forward and OMG there was a rifle there. HE JUMPED BACK, THERE IS A FIREARM IN YOUR TRUCK. Yeah, what's your point? I claimed it at the crossing booth and you have the note stating such in your hand. He looked at the form. On Your Way.
They used to always ask what your job was? Law Enforcement. Where is your gun? Some times multiple questions regarding my having a pistol with me. This was back before Canadian Customs were allowed to carry firearms and they would close the boarder crossings if there was so much as a rumor there was a crazy American thinking about crossing the northern boarder they manned with a gun.
ALSO NOTE: A couple things. We ran into a couple in Takini Hot Springs north of Whitehorse. They had attempted to return to the Yukon from Alaska via the Top of the World Hwy with a shotgun in their RV. They had submitted an application, paid a fee and been approved to transport a 12 gauge shotgun through Canada. This worked for them as they entered from the south. However when they attempted to re-enter east of TOK going to Dawson City they were turned back for the shotgun. So they had to return to Tok and obtain a shipping box from a firearms dealing hardware store and ship their shotgun home to a friend to hold till they returned home. They were not happy with Canadian Customs.
Also, if you've ever had a DUI or been convicted of DV Assault or most felonies don't waste your time going to the boarder. They will decline your entry into the country. They run criminal histories on all in the vehicle when you attempt to enter the country.
Also, expect to be stopped at random check points in Canada. Sobriety mostly but I was towing a cargo trailer once behind my truck with camper to inspect the cargo trailer to insure the trailer brakes were operational. Trailer was brand new so all was good to go. Before I could pull back onto Hwy 97 north the RCMP ran back over and asked if I could hold on a few minutes. Sure! He was inspecting a southbound trailer across the highway from me which was not up to par so he wanted to show the operator what he needed to do to meet their laws. They also run your license for a background criminal history check, wants/warrants etc.