A court challenge against National Party candidate selection rules could cause other political parties headaches if it succeeds.
Next week, the High Court will decide on a complaint from Roger Payne that the National Party board's rejection of him as a candidate was contrary to the Electoral Act
1993, which requires parties to follow "democratic procedures" when selecting candidates.
Mr Payne's nomination to stand in the South Island Selwyn electorate was rejected by the party's board under a power in its rules giving it "unfettered discretion" to discount potential candidates.
The outcome of the court decision will be closely watched by other political parties - most of which have some similar form of screening of potential candidates by their central executive.
Otago University law school associate professor Andrew Geddis said it was an important test case of a loosely worded provision in the Electoral Act.
The law requires parties to allow its grass roots membership and delegates to take part in selecting candidates but is unclear whether that participation was required at every stage of the selection process.
If the court found against National, other selections in which a similar process was used may also have to be reopened if there were complaints.
"It has the potential to blow up quite big, but that really hangs on what they judge thinks of some relatively obscure part of electoral law."
Act MP Heather Roy said such a provision was necessary to weed out unsuitable candidates.
But the party had not used the power this year.
Green Party co-leader Russel Norman said its executive could also veto choices including people in its candidates' pool, but the power was rarely used.
Mr Geddis said it was only a matter of time before a disgruntled candidate tested the provision.
