Ministers have won an appeal against a court ruling which could have widened the grounds for being granted asylum.
The Darfur region of Sudan has been wracked by conflict
The Law Lords upheld Home Secretary Jacqui Smith's complaint about the Court of Appeal's decision to overturn a tribunal ruling.
The tribunal said sending refugees to camps in the Sudanese region of Darfur was not "unduly harsh" resettlement.
The Appeal Court decision could have extended the grounds for asylum to the standard of living that would be faced.
The home secretary challenged the court's finding that resettling three Darfuri asylum seekers was unlawful.
The Court of Appeal based its ruling on oppressive conditions in the camps, lack of resources for survival and the change it would make to their lives.
Ms Smith has said she will review government policy on Sudan following a report from the Aegis Trust human rights group.
The organisation said there had been torture of failed Darfuri asylum seekers who had returned from the UK.
The three men, all aged in their 30s, had appealed against a decision by the Asylum and Immigration Tribunal that they could be sent back to Sudan.
Following the Lords' ruling, the Home Office said it would "continue to uphold Britain's proud tradition of providing humanitarian protection".
"We agree with today's decision by the House of Lords that people facing persecution in Darfur can safely and reasonably relocate to Khartoum," it said in a statement.
"We will do everything we can do to help those who do not need our protection to go home voluntarily."
'Torture and death'
The United Nations High Commission for Refugees (UNHCR) said the ruling referred to a "highly technical aspect of asylum law" concerning people displaced within their own country.
Bemma Donkoh, the UNHCR representative to the UK, said: "The need to assess an asylum application on its individual merits - an approach that UNHCR advocates - does not preclude consideration of the difficulties that certain people are likely to face if returned to a situation of internal displacement.
"UNHCR continues to recommend to states that no non-Arab Sudanese originating from Darfur should be forcibly returned until such time as there is a significant improvement in the security situation in Darfur."
Louise Roland-Gosselin, director of human rights campaign group Waging Peace, said the decision flew in the face of "the claims of our government to be concerned for the lives of the people of Darfur".
"Despite government rhetoric about the imperative to act, we continue to send those seeking asylum back to Khartoum to face almost certain torture and death," Ms Roland-Gosselin said.