DUBAI - Four months after President Hassan Rouhani's election, Iran is reviewing the house arrest of two opposition leaders, but conservatives may fear the consequences of freeing men who remain heroes to many Iranians.Mirhossein Mousavi and Mehdi Karoubi, candidates who led the "Green Movement" that disputed the 2009 re-election of Mahmoud Ahmadinejad, have never been charged with any crime. Yet both men, former top officials now in their 70s and in ill health, have been held under tight surveillance since early 2011.But now, as Iran seems keen to heal old conflicts both at home and with the West, their living conditions have been eased and their case referred to a powerful state security council. To some, this shows Iran's most powerful figure, Supreme Leader Ayatollah Ali Khamenei, wants to resolve the issue - although so far the council has had no contact with either opposition leader or their families.Under Ahmadinejad's hardline presidency, they were denounced as "seditionists" and accused of helping Iran's enemies to undermine the Islamic theocracy. Doors and windows of the house where Mousavi is held were welded shut, and both were allowed little contact with their families.But since Rouhani's election, they now enjoy weekly visits from their families. Relations with security guards have softened and access to specialist medical treatment improved."The political situation has completely changed since Mr Rouhani came to power and in some aspects the confinement of my father is absolutely better than before," said one of Karoubi's sons, Mohammad Taghi who lives in Britain. "But this confinement according to Iranian law is completely illegal. No doubt about it."Under Rouhani the atmosphere is very different both in Iran's troubled relations with the outside world and at home. Tehran has hinted at a possible readiness to scale back nuclear work - which it says is peaceful but the West fears is aimed at developing weapons - in exchange for relief from trade and financial sanctions which are crippling the Iranian economy.NO GUARANTEE OF RELEASEIn Iran, dozens of political prisoners have been pardoned and Rouhani seems intent on reversing the social and political restrictions imposed during Ahmadinejad's two terms in office.But the case of a Mousavi, who was prime minister for much of the 1980s, and Karoubi, a former speaker of parliament, is complex. Four years ago, huge crowds protested against an Ahmadinejad victory which they believed was rigged.Security forces put down the movement and in 2011 the two opposition leaders lost their freedom after calling for a rally in support of protests that were sweeping the Arab world.Earlier this month, Minister of Justice Mostafa Pour Mohammadi announced their cases were being re-examined by the Supreme National Security Council (SNSC).This body, which is responsible for setting defense and security policy, has undergone a reshuffle reflecting the changed times in Tehran. Both men's health problems will worry the clerical leadership, as any significant deterioration while they remain detained would arouse fury among their supporters. Nevertheless, this does not guarantee their release."The authorities simply don't know what the reaction would be. Mousavi and Karoubi are lionized figures and their hero status will go through the roof. The right-wing camp still has serious misgivings," said Siavush Randjbar-Daemi, an Iran expert at Britain's University of Manchester.Security agencies are likely to fear their release would provoke huge rallies in their support and disrupt Iran's new political chapter under Rouhani. Above all, supreme leader Khamenei is almost certainly intent on ensuring there is no repeat of the unrest in 2009 that eroded his authority and threatened the very existence of the Islamic Republic.IMPROVED CONDITIONSMehdi Karoubi, 76, is being held in a house in northern Tehran. He is now visited by his wife Fatemeh, two of his children and his grandchildren every Wednesday for several hours. During the visits, just one security guard is present in the room and the family can talk in relative privacy.Before the election families of both men went for months without any contact. "We were so worried. No one knew what was going on," Mohammad Taghi Karoubi said. During some visits up to eight guards were present and family members were not allowed any private contact. Any breach of the rules was punished by further visits being postponed.Karoubi keeps himself busy reading books his wife is allowed to bring and two newspapers he is given. He also spends time writing his diary.He has suffered serious back pain for the last two months and has trouble walking. After making a request, a doctor chosen by the family was allowed to treat him at the house. "It's a change. It took four to five weeks but at the end of the day, they let the doctor come," said Mohammad Taghi.In late July Karoubi senior was admitted to Tehran Heart Centre where he was treated for a blocked coronary artery.Early that month, 71-year-old Mousavi was also taken to the same hospital twice in 24 hours suffering from rapidly fluctuating blood pressure.Security guards escorted Mousavi, who suffered heart problems in mid 2012, to the hospital with his wife Zahra Rahnavard but refused to let him be formally admitted.Mousavi suffers from stomach, heart and leg problems. His health and well being is "at the mercy of security forces", Ardeshir Amir Arjomand an adviser to Mousavi, said from France."There is a certain amount of medical treatment but the family is still very concerned because the situation requires regular treatment in a calm atmosphere, without stress and by a doctor which the family trusts," said Arjomand.Mousavi and his wife now also have weekly visits from their daughters. "These are positive signs. We have new hope for the future," said Arjomand, referring to the referral of the case to the SNSC. "But there has been no judiciary procedure and their confinement amounts to an illegal imprisonment."A POLITICAL CHALLENGEThe SNSC comes under the presidency, giving Rouhani some influence over any decision on the two men's fate. Saeed Jalili, a hardline war veteran, was removed as its secretary in the reshuffle which installed several of Rouhani's most important cabinet members."The Council's new head, Ali Shamkhani, is someone who has a track record of going against the tide and being a frank and rational security official. It's a very different outlook to the Jalili period," said Randjbar-Daemi at Manchester university.However, Khamenei also appoints a number of important SNSC members, including the chiefs of the armed forces and Revolutionary Guards. These men are likely to avoid any decision to release if they fear this would lead to mass rallies. In any case, Khamenei must approve any decision the SNSC makes.The two opposition leaders' isolation has now lasted for more than 950 days and it appears that neither will promise to remain silent in return for their liberty."Such a condition is totally and utterly unacceptable," said Mohammad Taghi Karoubi. "During the last family visit, my father made it clear. He said, 'If I am a free man I will use all my rights as a free man. I will talk to my people, express my thanks and talk about the issues that people expect politicians to talk about. This is my job'."