Three landowners are suing the state over the law, which transferred pipeline regulation from the state's independent Public Service Commission to Gov. Dave Heineman.
More than 50 people turned out in front of a courthouse in Nebraska last week to support a court challenge to the legislation.
Pipeline company TransCanada aims to build part of the cross-border section of Keystone XL through Nebraska. The route through the state was revised to allay concerns over a groundwater aquifer.
Ken Winston, a Sierra Club advocate in Nebraska, was quoted Friday by the Lincoln (Nebraska) Journal Star as saying, "TransCanada got a bill passed that protects their rights and the use of eminent domain."
Randy Thompson, one of those filing the lawsuit, said state lawmakers declared "open season" on landowners with the legislation.
The federal government needs to sign off on cross-border sections of the pipeline, which is viewed by supporters as a way to ensure North American energy independence.
Detractors say the environmental risks associated with Canadian crude oil are too great to ignore.