And that's what I was told by MSP when I called, 11 years ago.
Of course, the nice officer I talked to went a little further. He told me I shouldn't try to go target shooting anywhere, or move the pistols out of my new home in Michigan until I have registered them. He explained if something bad happened, I could end up with more legal trouble than I'd probably want. I decided his advice was probably well intended, and more than likely true. Fortunately, it didn't take long for me to establish residency.
Fortunately not having a pistol registered is now only a civil infraction. Best bet if you want to cover all your bases is just to print out some RI-60's, and mail them in before you come in to the state (if your moving here).
Now as for visiting Detroit, like others have said, possession of a pistol without a CPL from your HOME STATE is illegal.
Some words of caution if you have never visited Detroit before since no one has mentioned it yet:
Coming to Detroit unarmed is extremely dangerous, Detroit statistically has a higher murder rate than the entire countries of Iraq, and Afghanistan combined, Detroit is one of the most dangerous, and crime ridden cities on Earth, come unarmed at your own risk.
If you do come to Detroit, stay inside the people mover tracks, this is the "Green Zone", it's heavily patrolled by police, and is relatively safe, the farther you get from the Green Zone the deeper in to Indian country you get, and the greater the danger, also stay inside at night, particularly if you are outside the Green Zone.
The suburbs are mostly safe, particularly the ones to the West, and North, though the outer ones are safer than the inner ones. You should avoid Lincoln Park, Highland Park, Redford, Wayne, and Westland, and any of the other smaller inner suburbs with the exception of those to the North.
Navigating the streets of Detroit is next to impossible, even with a map, and compass. Most street signs have been stolen, and many of the remaining ones are incorrect (sometimes deliberately). The city is riddled with one way streets, and they seem to appear at random. Service drives are non existent. There is not a single strait street in the city, the city completely lacks a traditional grid layout, and streets are seemingly laid out randomly, they end abruptly, cut off at weird angles, and randomly turn in to other streets, and one ways, there is no rhyme, or reason to it, and remember there are no signs for the most part, and the remaining ones are often wrong, or misleading. Additionally many of the streets, particularly the smaller ones are obstructed with debri, rubble, and burned cars, and many manhole covers are missing.
The residents of Detroit do not know how to drive, and can not be counted on to obey the rules of the road, traffic laws, signs, or signals or even common sense, and the pedestrians are just as stupid, and will often dart directly out in to traffic without even once looking for oncoming cars.
Do NOT get off the freeway to detour around unless you have no choice, as I mentioned, there is no such thing as a service drive, or grid in Detroit, getting back on to the freeway may be next to impossible, and will likely require you to drive many miles over random streets to get back to the freeway who's on ramp was just a half mile from where you got off. The last time I had to get off 94 for gas it took nearly a half hour to get back on to the freeway despite the on ramp being only a few hundred feet away as none of the streets go in a strait line, again there is no logic to the street layout in Detroit. On that same trip to the gas station, I ended up on a random dead end debris strewn street, and was nearly ambushed as someone rolled a tire across the road to block my path, I was able to swerve around it, but I spent the entire time with one hand on the wheel, and the other on my Glock.
I treat the entire area south of 8 Mile, and East of Telegraph as a no mans land, I do not go there unless necessary, and never unarmed. The city of Detroit is like the Lord Of The Flies, there is no civilization there, entire sections of the city look like something out of Mad max, or a scene from Red Dawn chain link fence across windows, razor wire on roofs, holes BLOWN in walls with the rubble, and debris strewn across the street, burned cars on the side of the road, collapsed roofs, it looks like an artillery strike. It's like driving through Beirut, or Grozny. The only thing missing is sandbags, and I'm sure there somewhere.