please read this....what a Wi DNR warden told me today

The way I'm interpreting what the warden is enforcing is that while on the water on the Wisconsin side, you're only allowed 5 in your possession.  In this case, it would be hard to prove to a warden that you did in fact catch them in Illinois.  But, I do believe you would still be over your limit considering you're traveling in WI waters.  The only boundary water I fish is the Mississippi and there is common ground between WI and MN on rules and limits.  It's surprising there is here as well if it's that close of a distance to travel to catch them.  ​

Many lakes have special size regulations, slot sizes, etc.

If I'm ever keeping fish from a body of water where the size and/or bag limit differs from the general regulations booklet, I take a picture with my phone that details the date, time, and lake.

I would think if a warden ever inquired what Lake you caught the fish in your possession at, simply show him a picture that shows the time, date, lake, and fish quantity.

I would think a simple step like that would clear up any questions...

Ticket or no ticket, it would be up to the warden to prove where the fish were caught. 

I'm just surprised the limit in Lake Michigan is still 5 after all these years. It's 15 in Illinois and in Geenbay, but 5 in L.M.  sure would simplify things if it was all the same. And on this same body of water, the Michigan side has a limit of 25 perch, wtf.

Probably the same thinking that if you bought weed legally in IL. and brought it back to Wisconsin where it is illegal.

The burden of proof should be on the warden. That's not what he implied.

So I could go to Lake Geneva and catch 25 perch and the warden would say....Perch limit in L MIch is 5. Here's your ticket. We have so many different size and keep limits on our waters his answer leaves me shaking my head.

Then there is possession limit. What if you drove to Zion, IL and launched and fished IL waters. You keep 15, drive across border. Possession limit in WI is 10 if from Lake Michigan. How could you or they prove where you caught them? 

It would be hard to prove where your fish were caught.
Obviously it would be no issue if both waters shared the same bag limits as you have both state fishing licenses.
I get your point tho.
When I lived on the Mississippi, I could travel WI waters and hunt ducks in MN, legally. As long as I had the appropriate licencing for the state I was hunting in. 

I see your logic and would even say if you have WI lice you should be able to keep 20, 15 IL & 5 WI. How do you prove where you caught them, though?
Same could be true on Mississippi River. Launch north of border, go down stream to IL, limit is 25, WI is 15.