Four gun control measures—two sponsored by Democrats, two by Republicans—failed in the Senate on Monday.

USA Today provides a brief overview of each amendment (to a DOJ spending bill):

► An amendment by Sen. Dianne Feinstein, D-Calif., would allow the attorney general to deny a gun sale to anyone if she has a “reasonable belief” — a lesser standard than “probable cause” — that the buyer was likely to engage in terrorism. The proposal is popularly known as the “no-fly, no-buy” amendment, but wouldn’t just apply to people on the “no fly” terrorist watch list.

► An Republican alternative by Sen. John Cornyn, R-Texas, which would require that law enforcement be alerted when anyone on the terror watch list attempts to buy a weapon from a licensed dealer. If the buyer has been investigated for terrorism within the past five years, the attorney general could block a sale for up to three days while a court reviews the sale.

► An amendment by Sen. Chuck Grassley, R-Iowa, would make it more difficult to add mentally ill people to the background check database, giving people suspected of serious mental illness a process to challenge that determination.

► An amendment by Sen. Chris Murphy, D-Conn., that would close the “gun show loophole” by requiring every gun purchaser to undergo a background check, and to expand the background check database.

Real Clear Politics has more on the two Republican proposals and the votes:

The second pair of amendments dealt with preventing terrorists from purchasing guns in the United States, a hot-button issue after the Orlando shooting. While there’s bipartisan support for the broad principle of blocking terrorists from having guns, there’s significant disagreement on the policy details. Sen. Dianne Feinstein, D-Calif., introduced an amendment that would allow the attorney general to block gun sales to any known or suspected terrorists. Republicans argue that the amendment is too broad, has no due process in place and would violate Second Amendment rights of people placed on the watch list accidentally.

That vote failed with 47 yes votes, including those of Republicans Kirk and Sen. Kelly Ayotte of New Hampshire, and 53 no votes, including Heitkamp as the lone Democratic dissenter.

Cornyn, the Republican whip, offered a counter-measure that would alert law enforcement when someone on the terror watch list attempted a firearm purchase. It would allow a 72-hour block on the purchase while requiring law enforcement officials to investigate and prove their case to a judge before permanently blocking the sale. Cornyn argued that the measure actually goes further because it would force an investigation of the individual; Democrats counter it would create an extremely difficult standard and time frame and is not a practical solution.

That measure failed with 53 yes votes, including two Democrats [Manchin (D-WV) and Donnelly (D-IN)], and 47 no votes, including three Republicans [Flake (R-AZ), Kirk (R-IL), and Collins (R-ME)]. [inserts via WaPo]

A fifth measure, being drafted by Susan Collins (R-ME) and Kelly Ayotte (R-NH), is being touted as a “compromise bill.” reports:

[Ayotte]  said she would vote to advance debate on the so-called “no fly, no buy” issue as a means toward passing a compromise bill she’s drafting with fellow Republican Sen. Susan Collins, of Maine.

“If you’re too dangerous to board a commercial plane, it stands to reason that you shouldn’t be able to buy a gun,” Ayotte said on the Senate floor Monday. “It’s simple as that and people on both sides of the aisle I think agree on that in principle.”

Yet people have been placed on these lists either by mistake, by being misidentified as someone on the list, or for a host of reasons unrelated to Islamic terrorism.  For example, Senator Ted Kennedy (D-MA) was misidentified as someone on the no-fly list, Civil Rights leader John Lewis was also placed on the list, as was Weekly Standard writer Stephen Hayes.  These are the cases that are widely reported because of the high profiles of the people involved; however, we’ve also seen reports of an 18-month-old toddler being on the no-fly list and many other such stories of retirees, 9-month-old babies, among others.

Not only are mistaken identity and “clerical error” problems with the “no fly, no buy” plan, but there is also the problem of the lack of due process involved when depriving someone of their Second Amendment rights.  Collins’ bill, however, includes an appeal process for someone blocked from buying a gun (apparently, that is when they will learn they are on the no-fly or selectee lists).

Boston. com continues:

Collins spokeswoman Annie Clark said the “compromise proposal,” which is expected to be introduced Tuesday, would block the sale of guns to people on two terrorist watch list subsets: the no-fly list, which prohibits individuals from boarding a plane, and the “selectee list,” which requires individuals to undergo additional screening before boarding.

. . . .   According to Clark, the proposal would additionally “provide due process by allowing an individual to appeal a decision blocking his or her purchase of a firearm, and, if successful, to be awarded attorney’s fees.”

Ayotte said Republican Sens. Jeff Flake, of Arizona, and Lindsey Graham, of South Carolina, had been working with Democrats on the bill. Neither, Ayotte nor Collins’s office named any specific Democrats on Monday.

You can read a version of the DHS report on the no-fly and selectee lists here.  The criteria for placement on both lists is redacted, however, and apparently still secret.