PORTLAND — Oregon’s domestic partnership law came under legal fire again Tuesday, as opponents tried to persuade three judges from the 9th U.S. Circuit Court of Appeals that elections officials had wrongly disqualified the issue from the November ballot.

A ruling is expected by the end of the month in a case that could have implications that reach far beyond Oregon. Should the judges rule in favor of the law’s opponents, states throughout the West could be forced to re-evaluate the process by which citizen-backed initiatives and referrals qualify for the ballot.

At issue is the arcane elections practice of statistical sampling of the signatures turned in to put a such a measure on the ballot.

Rather than verify each signature to determine that there are enough to merit a position on the ballot, elections officials in most states — including Oregon — pull a sample of the signatures and check them against those on a voter’s registration card. Signatures that don’t match are thrown out.

In the case at hand, Lemons v. Bradbury, about 30 Oregon voters have argued that their signatures were disqualified improperly.