Free migration is not limited to a certain time period, but has been more relevant and controversial in recent years, especially in the United States. In the U.S., it has become a more controversial topic since 9/11.Free migration is a concept to consider when comparing basic human rights and migration. "Constraining movement in most cases is therefore, unjustified and immoral". The topic of free migration is not a matter to be only exclusively debated amongst national governments of varying nations, but a worldwide discussion for all people of all nations on the debate of open borders and free migration. In that case, nations and people from all over the world can learn from each other where everyone is involved in the attempt to come to a just conclusion and solution to the problems surrounding both immigration and free migration alike.