Arc21 Court of Appeal ruling: What does it mean?

It has been 536 days since power-sharing in Northern Ireland collapsed - 536 days without ministers to oversee the running of Stormont's nine departments.

In the absence of an executive, civil servants were left uncertain about what decisions to take, and who should take them.

The long-running court case over the proposed Arc21 waste incinerator in County Antrim raised questions about exactly that conundrum.

The judgement upholding a ruling that a senior civil servant did not have the power to act without ministerial approval in the case of the incinerator could have massive implications for future governance in Northern Ireland.

Here are some of the key parts of the judgement and what they mean.

"Any decision which as a matter of convention or otherwise would normally go before the minister for approval lies beyond the competence of a senior civil servant in the absence of a minister."

Effectively, civil servants do not have the authority to take decisions usually reserved for a minister, even while the executive and assembly aren't functioning.

A civil servant's job description is to advise ministers and be accountable to them, and the judges agreed that any divergence from that even in circumstances where Stormont isn't functioning would be a "remarkable constitutional change" and a departure from what was stated in the 1998 Good Friday Agreement.

"The Court of Appeal agreed that the decision in this case is a cross-cutting decision and said that the 1998 act expressly attributes that function to the executive committee and provides a mechanism to ensure that the authority of ministers is limited accordingly."

' A cross-cutting decision' - basically a decision where two or more departments would have input into any project.

The appeal judges ruled that such was the environmental and political significance of the decision about whether or not to approve the incinerator plant, which during devolution would have been a decision that cut across several Stormont departments.

Decisions like that would normally be reserved for a minister to sign off on, or would be required to be brought to the entire executive to get the green light.

As a result of the ruling though, there is concern now from some political parties and business leaders that many other decisions that would be determined as significant or "cross-cutting" sitting in Stormont department in-trays awaiting approval could be left waiting an awful lot longer.

The North-South Interconnector is already facing a legal challenge on the same grounds as the incinerator, while Casement Park, the proposed new GAA stadium in west Belfast, the Belfast Transport Hub and Dalriadan gold mine are all waiting approval from the Department for Infrastructure.

"Observations on the limited powers available to senior civil servants in the absence of a minister are contained within the judgement, but it expressed no final view on the competence of departments to make decisions during periods when no minister is in place."

Despite the strong wording earlier in the ruling from the appeal judges about the limits on what civil servants can do, their conclusion is far from clear-cut.

When the appeal to the incinerator case was announced, the head of the Northern Ireland civil service, David Sterling, said it was important to get clarity on the powers available to civil servants in the absence of ministers.

But the waters appear even more muddied now, and politicians and businesses have turned their attention to the Secretary of State Karen Bradley, urging her to step in and bring in direct rule ministers from Westminster so that all of those big decisions can be taken.

But that in itself would bring with it a whole other series of implications for politics in Northern Ireland.