US cannot override Swedish or Finnish law by any means save from invading, Krister Sundelin explains:
NATO membership is also an international agreement between the current NATO members and the new NATO members, and in that membership agreement, the new members can specify anything which is not in the NATO treaty and both parties will accept.
Since neither nukes or American bases are mentioned in the NATO treaty, Finland (and Sweden) are completely free to specify that they do not want nuclear weapons on their territory.
This is not something new: Denmark and Norway already have that arrangement.
Never, US does not impose her weapons on NATO members.
The pictures above is a proof that US doesn’t force you to use its nuclear weapon. The only time a country could use American equipment is when they buy it. Otherwise, they make it themselves.
And that is the NATO tradition: each membership country builds its own defence systems.
We do make a point of making equipment compatible, so that we use the same type of 5.56 NATO round, the same 155 mm howitzer shells, the same kind of jet fuel or tank fuel, because it makes the logistics a heck of a lot easier.
Even Swedes made a point of making our own non-US jet fighters capable of air refuelling using the same kind of drogue and probe system that NATO uses – partially because some of our Gripen customers are NATO members, but also that Sweden already is a NATO partner.