THE battle between the UK and Scottish governments over the gender reform legislation could take months to resolve, a legal expert has said.

First Minister Nicola Sturgeon has said the move to use a Section 35 order by UK ministers would "inevitably end up in court", adding the Scottish Government will "vigorously defend” the legislation.

There is no process to appeal the issuing of the order and MPs will not have a vote on it in Parliament.

And unlike previous times where the UK Government has challenged Scottish legislation under a different section of the Scotland Act, the case will not automatically go to the Supreme Court.

READ MORE: First Minister: 'Inevitable' row over gender bill will go to court

Instead a judicial review is now expected to take place at the Court of Session in Edinburgh.

Dr Nick McKerrell, senior lecturer in law at Glasgow Caledonian University, said the Scottish Government was likely to challenge the order on the basis that it can be made in circumstances where devolved legislation makes “modifications of the law as it applies to reserved matters”.

“The Scottish Government could argue, and I would think will argue, their law does not modify the reserved matters law - which the UK Government have made clear in (Alister) Jack’s statement is the Equality Act,” he said.

“In a very literal sense that is true, because it doesn’t formally amend or change the Equality Act.

“They would argue their law does not modify the Equality Act in any way and because the UK Government are acting beyond their powers because they are using a process which is not relevant, because modification has not happened.”

McKerrell said that only those who have a direct "standing" in the case would be able to challenge it.

“You could argue ultimately it affects trans people and that is true,” he said.

“But the decision itself is to block the Scottish law gaining Royal Assent, so the organisation that has got direct standing on this is the Scottish Parliament and the Scottish Government.

“The Scottish Government because it is the Scottish Government’s law, and Scottish Parliament because it was the decision of the Scottish Parliament to pass the act.”

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When it comes to the timescale, McKerrell said a judicial review could be heard in around six weeks – but that decision can also be appealed all the way to the Supreme Court, a process which could take until the autumn.

As a Section 35 order has never been used before, the consequences of any court decision also have no precedent.

McKerrell said it could be result in negotiations to amend the legislation if the court decided the Section 35 order was made lawfully.

If it was ruled unlawful, the UK Government would have to find different reasons for issuing the order again – or seek to try another legal route.

“What could happen is the UK Government would then say we are referring it to the Supreme Court, under Section 33 (of the Scotland Act)”, he added.

“They might see that legal process as a way of resolving it.”