Not OP.
When she was originally brought in for questioning, there was an existing warrant that they ended up not holding her on due a birthdate mismatch on the warrant. This might be where this line of argument is coming from, as it seems reasonable that people with outstanding arrest warrants would not pass gun purchase background checks. It appears that at least in 2019 arrest warrants do not prevent you from buying a gun in Texas, I have not seen any reporting that specifically states that she was ineligible to purchase a firearm in Texas. It looks like Colin is legally in the clear here, although he may end up looking bad if it comes out that he bought the gun because he thought she was ineligible due to the warrant, even though she likely wasn’t. (Someone else can track down with the laws changed regarding this since 2019, but I doubt it.)
From: Fact-check: Can you pass a gun-purchase background check in Texas with an arrest warrant for murder?
“You can have an active warrant for your arrest for murder and legally pass a background check system in the state of Texas,” Hinojosa said.
In a press conference Wednesday, police officials said that their “report management system” showed Armstrong to have a birth date in April that did not match the date of birth on an unrelated misdemeanor warrant that police used to bring her in for questioning.
The 34-year-old Armstrong, whose date of birth is November 21, 1987, was initially questioned by the Lone Star Fugitive Task Force when the office discovered an outstanding class-B warrant for her arrest.