There is a general tendency nowadays to form groups by some agents for 'Umrah. The problem with this method of 'Umrah is that some of the ladies also want to perform 'Umrah but they do not have a Mahram to accompany them. In the process, what the agents do is to declare some males in the group as Mahram of these ladies so that the official requirement is fulfilled. I wanted to know whether this kind of subterfuge is allowable in Islam. A good aspect of forming these groups could be that these groups consist of subgroups of ladies who then perform the 'Umrah rituals quite satisfactorily and independently, which serve the real purpose of the company of a Mahram.
Before commenting on your specific question I would like you to appreciate that the Islamic Shari'ah has not held it compulsory for women to be accompanied by a Mahram during their travel to perform Hajj or 'Umrah. We believe that some of the jurists have misconstrued a saying of the Holy Prophet (sws) in this regard. In our opinion, the Shari'ah does not hinder women from performing Hajj without being accompanied by a Mahram relation. No doubt the Holy Prophet (sws) recommended women to avoid traveling alone. This recommendation is not principally related to traveling for Hajj, rather it is a social advice he gave keeping in view the circumstances of those times.
A study of all the traditions leads to the conclusion that the Prophet (sws) recommended women not to travel alone because of the grave dangers it entailed. Such a journey could endanger both a woman's life and her repute. The circumstances at that time were not appropriate for even men to set out on journeys easily. These factors may not be present today with the development of organized and disciplined means of transportation, however, a lady must take the decision herself whether to travel alone or not keeping in view these aspects. If she is satisfied that her travel is risk free and she decides to travel alone, she would not be violating the directive of the Prophet (sws).
This is our understanding of the issue. However, this does not alter any thing for these people, as, we know that women - without the company of Mahram relations - are generally refused visa for Hajj and/or 'Umrah by the Saudi government. They regard it to be a directive of the Shari'ah and they have very right to promulgate decrees they believe to be the part of the Shari'ah or a necessary administrative requirement. As a principle, it would not be right to breach legal requirements and produce fake certificates. Those who dare do this must know that they have to face the Almighty on the Day of Judgement and account for all their actions.