Measure 7, approved by 53% of voters in November, requires "payment to landowner if government regulation reduces property value." It's supporters say it will cost government no more than $50 million to $100 million per year. It's opponents put the annual impact at closer to $5.4 billion because they believe that as many as 90 types of laws - from building height limits to requirements for public restrooms to solid waste disposal restrictions - may qualify for Measure 7 claims.

To get the preliminary injunction, lawyers must convince the judge that Measure 7 would cause "irreparable damage" if allowed to take effect, and that their lawsuit has a "substantial likelihood of success" at trial. Judge Paul Lipscomb's ruling was in response to a lawsuit filed last week by the mayors of Salem and Jacksonville, and Audrey McCall, widow of former Gov. Tom McCall, who is credited with designing Oregon's vaunted system of land-use and environmental rules. A second lawsuit challenging the measure's constitutionality was filed Tuesday in Marion County Circuit Court by the League of Oregon Cities and others.

All of the legal challenges to Measure 7 are technical in nature. One argument is that it contains two or more "substantive and not closely-related" changes to the constitution and therefore violates the constitution's "single subject" rule for amendments. Another is that the measure itself does not contain the "full text" of the amendment, and a third is that the measure is not a proper amendment because it is advisory in nature.

Today, the Oregon attorney general's office - which has had some 15 lawyers working on the issue since its passage – is expected to release an opinion on the legal scope and meaning of Measure 7. The report is meant to help guide cities and counties, many of whom have already begin approving procedures for dealing with Measure 7 claims, and the fees they will charge to process the claims. The fees have ranged from a low of $200 in Pendleton to a high of $3,500 in Fairview, near Portland.

The possibility of the Legislature taking up the issue in January is likely. - which would define its scope and set statewide standards for implementation – is being discussed by members of the state Legislature. If the court challenges are ultimately unsuccessful, the Legislature is expected to take up the matter when it meets in January.

Meanwhile, one corporation has already filed a claim, and several other individuals and corporations are preparing for or considering the option. A mining company denied an expansion permit last month filed a lawsuit against Jackson County and the City of Jacksonville. The company is seeking $50 million in compensation under Measure 7.