A county in southern Missouri will lower flags in front of certain buildings during a particular date for an entire year to mourn the US Supreme Court's recent decision to legalise same-sex marriage across the country.

The lowering of the flags will be undertaken after the Dent County Commission, which is composed of three Republican members, unanimously approved a proposal on Monday to observe a full year of "mourning" over the legalisation of gay marriage.

Presiding Commissioner Darrell Skiles made the proposal, which was supported by Commissioners Gary Larson and Commissioner Dennis Purcell.

"All who see these flags at this lowered position be reminded of this despicable Supreme Court travesty," Skiles said.

Due to this, flags at the Dent County Courthouse and the Judicial Building will be lowered below half-staff every 26th of each month for a year, running from July to June.

"It ain't what our Bible tells us. It's against God's plan," Larson said.

Before proposing the lowering of flags to mourn the Supreme Court decision, Skiles also filed a letter into the public record detailing his opposition to the legalisation of same-sex marriage in America.

Skiles described the ruling as "the US high court's stamp of approval of what God speaks of as an abomination."

The commission's decision, however, was met with opposition by some of the county's residents. A petition called "Stop Act of Mourning Gay Marriage By Lowering Flags Below Half Mast" was even created online by Salem resident Alex Sellers.

"While it is understood that individual commissioners may disagree with this Supreme Court ruling and have every right to voice their individual opinions, it is inappropriate for them to take action such as that described which projects their opinions as those of the entire community," Sellers wrote in his online petition.