A straight couple attempting to intervene in a federal case challenging Kansas' ban on gay marriage claims allowing such unions would be tantamount to seizing their property.

On Wednesday, Philip and Sandra Unruh filed a motion to intervene in the case, arguing that marriage equality would violate their 5th Amendment rights.

According to the AP, a hearing in the case scheduled for Friday was canceled and plaintiffs have until Monday to file last-minute briefs.

“The Unruhs have an inalienable property right in their marriage that is protected by the 5th Amendment of the United States Constitution, the Kansas Constitution and related Kansas Statutes,” states the brief, provided by Equality Case Files.

“If the Plaintiffs are successful in their causes of action, the meaning of marriage will be so fundamentally and profoundly changed that the Unruh's will experience a taking of their property rights in marriage without due process of law.”

The couple contends that allowing gay couples to marry would be “a departure from the joy and celebration normally associated with the word marriage.”

Kansas is one of three holdout states that are refusing to comply with appellate court rulings declaring state marriage bans unconstitutional. The other two states are South Carolina and Montana.

(Related: Kansas Gov. Sam Brownback vows to defend state's gay marriage ban.)