A Texas congressman introduced legislation Thursday to get Chris Kyle, the man who inspired the movie “American Sniper,” the Medal of Honor, two days after a Marine veteran was convicted of killing him and another man two years ago. But history suggests the effort faces significant challenges, especially in an era where it nearly always goes to a service member who performed a single, extraordinary act of valor.

Rep. Roger Williams (R.Tex.) introduced the bill, which would authorize President Obama to award the nation’s highest award for combat valor to Kyle. He was nicknamed “The Legend,” and is often called the most deadly sniper in U.S. military history with at least 160 confirmed enemy kills.

“Chris gave the ultimate sacrifice and served his nation with distinction and bravery while saving countless American lives,” said Williams. “There is no doubt that this true American hero is worthy of our nation’s highest military honor. While the Medal of Honor will not bring back a husband, father, son and a model Texan, we owe Chris Kyle and his family a great deal of gratitude for his relentless devotion to his country.”

Kyle, 38, and his friend Chad Littlefield, 35, were killed by Eddie Ray Routh, 27, on a Texas rifle range on Feb. 2, 2013. Routh pleaded not guilty by reason of insanity, but a jury in Stephenville, Tex., unanimously convicted him of first-degree murder on Tuesday night.

Kyle already is highly decorated for his heroism in combat. He received two prestigious Silver Stars, which are two levels below the Medal of Honor, and five Bronze Stars with V device for valor. Kyle left the military in 2009, and released his memoir “American Sniper” in January 2012.

Williams, whose district includes part of the county where Kyle was killed, said in a news release that on a number of occasions, legislation has been introduced to waive restrictions and encourage the president to award the Medal of Honor.

But it’s more complicated than that. As a Congressional Research Service paper cited by Williams states, when Congress has waived restrictions to pave the way for Medals of Honor in the past, it is usually because there is a belief that a single act of heroism on the battlefield was overlooked.

“In a number of occasions, legislation has been offered to waive certain restrictions and to encourage the President to award the Medal of Honor to particular individuals,” said the CRS paper, published in September.

“Generally speaking, this type of legislation is rarely enacted,” the paper continued. “In a very limited number of cases, the medal has been awarded outside the legal restrictions concerning time limits. These cases are often based on technical errors, lost documents or eyewitness accounts, or other factors that justify reconsideration. These cases, however, represent the exception and not the rule.”

In one example, Congress approved legislation in 1996 to award seven black soldiers the Medal of Honor for heroism during World War II. It was widely believed that racial discrimination had led to them not being recognized for their valor. The awards were bestowed a year later.

More recently, Obama awarded Medals of Honor in September to two soldiers who served in Vietnam. In both cases, the awards came after congressmen wrote to the Army asking for them to investigate the cases again, in light of new information that was released.

Cases like those are extremely rare, however, and the military remains fiercely protective of the standards it takes to receive Medal of Honor. For Kyle to receive the Medal of Honor, it would require a significant departure from the way awards have been reviewed for years.