I would have to agree that the advice of your attorney would be a great place to start. Also, you might want to look up the condo association's rules because there may be provisions as to how many people can reside in a condo unit based on the number of bedrooms.
All of this assumes that you are the owner and the unit is a condo/coop.
Certainly, you, as the owner, have a right to refuse to put up a door to create a bedroom out of the living room.
You can also limit the number of people living in the unit - and........your HOA might even have restrictions in place regarding this. Check that out.
Of course, for any legal advice, you can always reach out to a real estate attorney, but, you own a condo, not a rental building, so, imo, you can set your own restrictions as to how many may reside there.
As long as you're not breaking any Fair Housing laws, your 1 bedroom unit can remain a 1 bedroom unit!