Here's some information on guns in Canada so we are all on the same page about "gun dealers" and gun "trafficking" etc.
The Firearms Act lays out the Federal regs on guns.
A person in Canada(resident or Citizen) must have a RCMP background check, two references(to be interviewed by RCMP) a signed permission from the current and previous spouse and attend and pass the PAL (Possession and Acquisition License) course, written exam and skill test or challenge test and pass just to own, posses and purchase certain long guns. At the time we are covering here, the Long Gun Registry boondoggle was in effect, so all long guns were registered with the RCMP and accessible by all LE from the patrol car.
For handguns the laws were the same except they are deemed Restricted and the PAL for them is called a RPAL and they have to be stored differently(more ridiculously than long guns) and one has to seek permission in writing from the CFO in Orillia to transport the gun ANYWHERE and must receive and carry the ATT paperwork along with the handgun straight to and straight from the "stated on the paperwork location and in that time frame ONLY"
Of course, this is far a non criminal, upstanding, law abiding residents and citizens of Canada. There is no law for criminals, but we know that.
Now, if I as a resident or citizen of Canada sell a long gun within Canada under the law, I must sell only to another resident/citizen who is legally permitted to posses, purchase and own that gun. ie they have to have a current PAL issued by RCMP, I must verify that and at the time we are speaking of with DM/WM do transfer paperwork with the CFO in Orillia in order to re-register the long gun in the new PAL(owner's) name, address, etc. Handguns are similar only more restrictive.
Now, the good part. If I am simply slow in renewing, Canada Post is slow, RCMP is slow in sending renewal, or I let it expire, I am immediately a felon, with a mandatory jail term and fine. You can't even make this ridiculous crap up.
Or less say I sell a long gun to a person without validating, doing all the paperwork, etc. to make sure the buyer has a PAL, I am immediately a "gun Trafficker" and he owns an "illegal gun" and we are both in serious trouble.
Oh by the way, the criminal scum of Canada don't lose any sleep over these insane rules, as they don't abide by them anyway and we simply create automatic criminals out of pillars of the community with these arcane laws.
It's even worse WRT a handgun.......
So take it with a grain of salt when using what the Canadian Police wording is(gun dealer, gun trafficker, illegal gun yada yada.) It may not be as nefarious as it sounds.
On the other hand there is a problem with criminals obtaining guns in Canada and the US illegally and in the US legally, then transporting them to Canada for sale illegally.(usually handguns)
In summary, if DM had no PAL, or the seller had no PAL, or if the paperwork wasn't correctly done everything became illegal and thus "illegal gun", "gun trafficking" etc, etc. Same thing with handgun only RPAL in place of PAL and more paperwork done and received prior to handing gun to buyer, ATT paperwork for buyer prior to transport home, etc.
Currently there is no longer millions of dollars being wasted on the long gun boondoggle. It's simply two PAL holders exchanging a gun and money after determining the buyer has a PAL. If a PAL holder purchases from a gun store it is the same, seeing the PAL, selling the long gun and no Federal Registry.
There are some nuances, with the Bantario CFO making up his own version of the law, but court cases are pending on that.
One last note...a person visiting Canada can bring guns into Canada legally by declaring them at the border and or obtain a PAL through normal means.
Hard to figure exactly what happened with DM/WM. If WM had a legal/illegal gun, why not just use it? If WM had no gun and DM need to get one, he obviously didn't grasp the convoluted BS of Canadian gun ownership/registry etc. at the time, if he randomly purchase a gun to do the deed.