There is a mechanism in the Northern Ireland Assembly that is designed to protect minority interests. It is called a petition of concern. Any 30 MLAs can call for one on any issue up for debate.

What it means that instead of simple majority the motion for debate requires 60% of the chamber and 40% of both the Unionist and Nationalist designations.

You may ask why I have highlighted this at the top of this post. The answer is to do with a debate before the Assembly on Monday 1 October, a debate on Equal Marriage, a motion largely similar to our own party policy, except it is calling on the Office of the First Minister and deputy First Minister to come up with the details, including stringent protections for religious groups that don’t want to carry out same sex marriage.

So a motion aiming at bringing about something enhancing for a minority group is going to be subject to a petition of concern. What is more the minority group in question is one that has long work across the ‘traditional’ divides in Northern Ireland to fight for their own minority and its concerns.

The 30 moving this petition of concern all come from the DUP, the largest party in the Assembly, and the only party of the executive to have come out totally opposed to marriage equality.

This weekend members of the DUP will be celebrating the Ulster Covenant which sought to defend by any means necessary the cherished equal citizenship with in the UK for the people of Ulster. This petition of concern, plus their negative attitude to lifting the MSM blood ban and allowing adoption by gay and lesbian couples adds the caveat that they only cherish equality for the citizens of Ulster with the rest of the UK if they are straight.

The DUP have 68% of all the Unionist designated MLAs. Effectively their petition of concern if the vote on Monday is three line whipped by their party could defeat the motion even if the 60% majority was reached. A misappropriation of power, and certainly as described elsewhere in the Ulster Covenant a subversion of civil and religious freedom.

But surely in this case the cross community support should only require 40% of the straight MLAs and 40% of the LGBT ones.

For the record there are no openly LGBT MLAs currently in the Assembly.

If you are in Northern Ireland, or know anyone in Northern Ireland write or get them to write to all their MLAs, even those in the DUP. Ask them that if they are not content with the language of the motion, to abstain and work with the proposers and Office of the First Minister and Deputy First Minister to make it workable for all.

* Stephen Glenn is the Chair of the Northern Ireland Liberal Democrats and a member of the Alliance Party. He has stood as a Westminster Candidate for the Lib Dems on three occasions.