Car dealerships would have to take a day off under a bill approved 70-25 by the Utah Legislature on Wednesday.
Senate Bill 163 would require dealerships to choose Saturday or Sunday to shut down.
Because Saturday is dealers' biggest sales day, the dealers are expected to close Sunday — a day when members of Utah's predominate faith, The Church of Jesus Christ of Latter-day Saints, attend church.
Utah's major car dealerships requested the blue law to impose conformity in the business.
Disobeying the blue law would bring escalating fines — $100 on the first, $250 on the second and $1,000 on the third offense in a year.
Fines would be assessed for each vehicle a dealer sells or offers to sell or lease in violation of the law.
The Senate voted 25-1 to approve Sen. Paul Juander's bill early last month. Juander is a Salt Lake City Democrat.
But when the House gave its 49-21 approval Wednesday, it added a "hardship" amendment that would allow dealers to help a distressed customer on Sundays with car repairs, parts or car rentals.
The Senate voted 21-4 to approve the amended bill on Wednesday.
Opponents argued the Legislature had no business dictating when a dealership should conduct business.
"If an automobile dealership wants to be closed on Sunday, they can be closed on Sunday," said Rep. Patricia Arent, D-Salt Lake City.
The bill doesn't accommodate everyone. Members of the Jewish faith take their Sabbath on Saturdays.
"Maybe we'd like the opportunity to shop on Sundays," Arent said.
Rep. Mary Carlson, D-Salt Lake City, said the Legislature was opening a Pandora's box that will have other businesses clamoring for their own blue laws.