What nations are you talking about? E.g. in Germany, you can buy up to 7kW of panels, screw them onto your roof, wire them up with controller and battery and feed up to 800W into local grid, no one is gonna stop you or anything (only thing you need to do is register online with the grid operator if you have >2kW of panels).
Legislation is, in fact, specifically made so people (i.e. landlord) actually can't easily stop you from doing this.
Not quite as I understand it. At the low end, a couple of panels, yes. Beyond 960W of panels you will still need an an electrician rather than just the Schuko plug.
It's not clear to me why, for example, 2kW of panels which are also limited to 800W need need the special plug.
Hopefully I'm wrong!
"With a standard Schuko plug, a maximum of 960 watts peak is allowed on the DC side, regulated by DIN VDE V 0126-95. With the Wieland connector, a special feed-in socket, the limit increases to 2,000 watts peak. Anyone wanting to operate a system with up to 7,000 watts of module power will need a permanently installed feed-in socket, thus entering a range that is technically possible but also more complex to implement."
The limits in power you can install, power you can inject to the grid and power you can just directly sell to neighbours through a micro-grid (zeeo, as it's illegal) tell quite the story.
Legislation is, in fact, specifically made so people (i.e. landlord) actually can't easily stop you from doing this.