As mentioned in an earlier post the municipality within whose borders the real estate is situated may have a right to step in as buyer on the same terms and conditions as the buyer who entered into the purchase contract with the seller.
Also mentioned earlier here purchases of tenement buildings may require separate approval according to the Act on Acquisitions of Tenement Buildings (I have not found any English translation). The buyer must notify the transfer to the municipality in which the real estate is situated. When the notification has been made, the municipality decides whether the transfer needs to be approved by the local
Rent Tribunal. Such approval will be granted after the Tribunal has found that the buyer has a long-term ambition with his investment and also the ability to manage the tenement building in an acceptable manner.
If the object of the purchase is agricultural land and land for forestry an approval is needed from the County Administration according to the Swedish Land Acquisition Act (I have not found any English translation).