Billström began his studies in Lund in the Philosophy Department, where he read 20 points scientific basics for Victoria Höög.

In April 2005, Billström became a member of the Social Security Committee and Moderate Party spokesperson on issues related to migration and integration.

Once it took office in October 2006, the Reinfeldt Cabinet set a new aim for Swedish migration policy, which was to increase the opportunities for labour immigration.

Billström emphasised the importance of creating a balance in the policy area where asylum issues often dominate.

[4] The government implemented, on 1 August 2007, a re-establishment support to facilitate the repatriation of those who have had their asylum applications rejected.

He emphasised the need for a very strong common asylum and migration policy, and that this could give more Iraqis in need of protection to access this.

The work was given a start with the article that Billström wrote with Cecilia Malmström in the Swedish newspaper Svenska Dagbladet.

[8] From 30 March until 4 April 2007, Billström, as the first European Minister for Migration and Asylum Policy, made a trip to Syria and Jordan to create a picture of the situation of the Iraqi refugees residing there.

[9] In classified documents revealed by Wikileaks, Billström, together with Carl Bildt during the two men's visit to the American Ambassador Ryan Crocker in Baghdad in 2007, reported the Iraqi refugee situation in Sweden, specifically mentioning honour killings and the Swedish opinion of restricting immigration.

[13] The right-wing Sweden Democrats party leader Jimmie Åkesson welcomed Billström's statement and said "that he was on the right track".

[13] In the early afternoon on the same day, Billström officially apologised for his statement and said that his words came out in the wrong way, and that what he said was not what he really meant.

[18] On 29 August 2024, during an interview on the Russo-Ukrainian conflict, he stated Swedish authorities including himself wished for a regime change in Russia.

[21] Billström served as Foreign Minister during Swedens historic entry into the North Atlantic Treaty Organization and a priority during his tenure was to secure membership ratification from Turkey and Hungary, who had both previously refused to approve Swedens membership after its application in 2022.