LINCOLN, Neb. (AP) — A group that wants to legalize medical marijuana in Nebraska sued the state on Monday to try to overturn a requirement that makes it harder to qualify for the ballot by forcing petitioners to get signatures from a large number rural counties.

The federal lawsuit comes after the group Nebraskans for Medical Marijuana lost one of its biggest donors, forcing the campaign to rely primarily on volunteers as it scrambles to place the issue on the November general election ballot.

Organizers have until July 7 to gather roughly 87,000 signatures from registered voters.

The Nebraska Constitution also requires those signatures to come from at least 5% of registered voters in 38 of the state’s 93 counties.