Well, that's true sort of. For the vast majority of the city's territory, the local government can do things like use police, charge taxes, design the streets (sometimes!), regulate the buildings and how people use land, and other things like that.
However! There are three exceptions, places where Saint Paul has very little power even within its own boundaries. These are the mini-kingdoms in our midst, places where Public Works or the assessor or the zoning code dares not tread.
#1: The State Fair (230 acres)
So, yeah, what city is the State Fair in anyway?
Most people would say Falcon Heights, but they are sort of not even in Falcon Heights either. They are their own government.
Como Avenue at the south edge of the Fairground is technically part of Saint Paul, however every year for two weeks the powers that be at the State Fair just do whatever they want to the street, without so much as consulting or maybe even informing the City. Often that means erasing the bike lane, even if cars don't use the extra traffic lane.
Basically, the State Fair does whatever it wants with their land and is accountable to nobody. Falcon Heights has no say over the Fair either. They are controlled by a shadowy cult, and nobody can criticize them lest they be declared un-Minnesotan and banished.
#2: The University of Minnesota (.62 square miles)
As any administrator will quickly tell you, the University of Minnesota is older than the state itself and they basically do whatever they want with their two campuses. They have their own police force, their own transit system, and their own private street (the "transitway") which they control. They also have vast sums of money with which to buy up property around their campuses.
God help the poor planner who has to reach out to anyone within the University's Byzantine bureaucratic administration if they want to coordinate on something like street changes, a bike lane, or anything else. They do whatever they want, and the best that a city hosting the U can do is to pray for their favor.
#3: The State Capitol Area (.5 square miles)
Back in the late 1960s, the State Government and the City of Saint Paul agreed to bequeath a large portion of the city on the northwest edge of downtown into the hands of a state government committee called the Capital Area Architectural and Planning Board. This extends, by the way, into downtown proper and all the way over to the Cathedral doorstep. From that point on, the vast majority of the land became parking lots, grey office buildings connected by tunnels, and empty green grass with statues in them.
There's nothing the city of Saint Paul can do about it either. Huge areas like the Rice Street Sears site are simply out of the hands of city planners. Historic buildings like the Ford Building are prone the whims of administrators who work in a brutalist structure accountable to some Greater Minnesota legislators and maybe, if you're lucky, the Lieutenant Governor.
These are the three fiefdoms of Saint Paul, parts of the city that play by their own rules, where the city staff or mayor's office can only beg for favor. There are smaller less-powerful or contiguous kingdoms and duchies as well, like the University of St. Thomas, Bill McGuire, the Metropolitan Airports Commission, the Mississippi River Critical Area, the Ford Motor Company, the Mancini family, or the Canada Pacific railyards.
One only hopes that the nameless rulers of these vast swaths will be beneficent.