So they can get the records??
yes
without a subpoena
yes. If they are available to the public which I believe all records in the LOC are (except active administration records or records deemed top secret).
I'm not sure what the status of these records are but I can't imagine that publication records from 30 years ago are either secret or relevent to the current administration.
Now, my experience with the LOC is very limited so maybe someone with more experience can add to this?