Judges rejected an appeal by families who argued that the rules breached their human right to a family life.
As of 2012, Britons must earn more than £18,600 before a husband or wife from outside the European Economic Area (EEA) can settle in the UK.
Judges criticised this threshold as "defective" and a cause of "hardship".
The seven justices sitting on the case found those rules did not take sufficient account of the welfare of the children involved, or of alternative sources of income.
http://www.bbc.co.uk/news/uk-39050664
The justices also acknowledge that that the rule does present a serious obstacle to their enjoying family life together and may provide a permanent obstacle to many couples because those earning less than £18,600 are unlikely to amass sufficient savings to make good the shortfall. Women and particularly those from minority ethnic groups will be particularly hit because of the gender pay gap.
But they have ruled that the £18,600 threshold is a legitimate part of an overall strategy aimed at reducing net migration. Its particular aims are no doubt entirely legitimate to ensure, as far as practicable, that the couple do not have recourse to welfare benefits and have sufficient resources to be able to play a full part of British life. They say that, given that is a legitimate aim, it not possible to say that a less intrusive measure should have been adopted.
Immigration welfare campaigners took comfort in the supreme courts findings that the rule was causing hardship to thousands of families and that the interests of children needed to be reconsidered.
Saira Grant, chief executive of the Joint Council for the Welfare of Immigrants, said: This judgment is a real victory for families especially those with children. For five years JCWI has been working with affected families and has been trying to persuade the government to abandon the family migration rules it introduced in 2012 because they are tearing families apart and significantly harming children.
https://www.theguardian.com/law/2017/feb/22/supreme-court-backs-minimum-income-rule-for-non-european-spouses