For the past five days, 1,000 female Nigerian pilgrims have been detained at an airport and various detention facilities in Saudi Arabia. They arrived in the country to conduct the annual pilgrimage, the hajj, a duty that every Muslim must fulfil once in their lifetime if they can afford to do so. Despite the fact that they had valid hajj visas, Saudi authorities would not allow them into the country as they were unaccompanied by male guardians (mahrams). While about 200 have already been sent back, the rest remain, awaiting a resolution of the matter between the Nigerian and Saudi governments.

The issue has precipitated a diplomatic spat between the two countries. A spokesman for the Nigerian vice-presidential office said he had received reports that the women were being subjected to "dehumanising treatment", being deprived of food and forced to sleep on cold floors. Paradoxically, and hypocritically, the women are being subjected to the very dishonour that a male guardian is allegedly required to protect them against.

Saudi Arabia prides itself on being "the custodian of the two holy mosques". Every year, the country hosts up to 3 million pilgrims as they perform the holy rite. It is a political and logistical feat, and Saudi Arabia has invested heavily in hajj infrastructure. However, the hajj is blighted with practical and logistical failures. And female pilgrims are often disproportionately affected, as they fall foul of arbitrary legal innovations and immigration disarray.

While the mahram requirement is notoriously well known, its application has been erratic. Female members of my family were sent back for not having a mahram as far back as the 1980s, but since then it has been common for women to be allowed to travel in convoys, sponsored by their diplomatic missions or equivalent authority. It seems that Saudis themselves admit that this is a new enforcement of the letter of the law: the Saudi ambassador in Abuja said that they had been "flexible in the past", but had decided to apply the law this time. To add to the humiliation, the implication that these women are not complying with religious law (of which Saudis believe their interpretation is the only arbiter) is insulting in the extreme: to want to complete the hajj at all (not to mention incurring the significant costs and physical hardship) would suggest a certain level of committed religious observance. In addition, the mahram rule is applied in its current extreme form only in Saudi Arabia. It is by no means a universal Islamic stipulation that other Muslims with different religious cultures would adopt, especially on a hajj trip lasting three days.

It is not the first time that female pilgrims have fallen victim to Saudi Arabia's random legislation. Last year, based on some internalised cultural stereotype, Saudis banned Moroccan women of a certain age from the umrah, a shorter pilgrimage, even if they were accompanied by mahrams, because of a belief that they were of loose morals and would somehow slip through the (very tight noose) of the umrah visa and entice Saudi men into underground prostitution rings.

Both incidents reek of national and racial discrimination. Nigerian officials claim that only Nigerian women were screened and subjected to such treatment. Unfortunately, in a region where there is sensitivity about the treatment of black Muslims – the term abda (slave) is one I heard often while living there – the cordoning off and manhandling of hundreds of black Muslim women looks very bad.

As the kingdom deported several thousand Nigerian overstayers last year, the mahram issue may well be a ham-fisted cover for a pre-emptive crackdown on immigration. Though it is perfectly within the kingdom's rights to apply entry conditions, it is unreasonable to do it under false pretences.

Whether it is the result of clumsy instruction from above or airport officials acting stubbornly and forcing the government to back them, the incident and the scores of angry women arriving in Nigeria and venting their ire to international media are an embarrassment to the Saudis at the beginning of hajj season.