By Eliott C. McLaughlin

CNN

(CNN) -- Tennessee's kidnapping law is a little ... well, toothless when it comes to youngsters the age of Elizabeth Thomas, the 15-year-old allegedly abducted by her former teacher, according to the prosecutor in the case.

District Attorney Brent Cooper of the 22nd Judicial Circuit wants to change that, and he hopes state lawmakers consider Elizabeth's case when they convene next year, he told CNN on Tuesday. Through an attorney, Elizabeth's father, Anthony Thomas, said he wants the law changed immediately.

The way it's written now, the statute lets children older than 12 decide whether to leave their families, unless their removal or confinement "is accomplished by force, threat or fraud."

Police say 50-year-old Tad Cummins, who taught Elizabeth in a forensics class at Culleoka Unit School, absconded with the freshman March 13, weeks after a student claimed to see the two kissing in Cummins' classroom.

The investigation led authorities to Decatur, Alabama, later that day before the two vanished.

As it stands, to prove the kidnapping of a victim who is 12 or older, Cooper said, he'd have to prove that Elizabeth was unlawfully removed or had her freedom restricted.

Further, to prove that Elizabeth was unlawfully removed, he'd need to demonstrate to a jury that Cummins employed "force, coercion, fraud or something to that effect," the prosecutor said.

"What we run into here, of course, is this child is 15 and, according to reports, at least initially, she left of her own free will," he said.

The issue was especially concerning at the outset of the investigation, Cooper said. Cummins was charged only with sexual contact with a minor by an authority figure, a misdemeanor. Investigators worried that if police stopped the pair out of state, they'd be released because authorities couldn't detain them, let alone extradite Cummins, on a misdemeanor warrant.

Cooper ultimately felt comfortable adding the aggravated kidnapping charge after deciding that Cummins allegedly groomed his victim and was armed, the latter being a prerequisite for aggravated kidnapping. (Grooming is the act of establishing a connection with a child with the goal of defusing his or her inhibitions toward sexual abuse.)

The prosecutor said the present law could pose obstacles once he has Cummins in a courtroom.

"Under current law, it's really going to depend what the testimony of Ms. Thomas is," Cooper said, explaining that if she claims she left on her own volition, the defense will argue Cummins is not guilty of kidnapping.

Cooper will then have to introduce circumstantial evidence that Elizabeth was coerced. The district attorney is confident the communications between Elizabeth and Cummins show "he was definitely trying to influence her in his favor," he said.

"This grown man was using his knowledge and life experience to basically attract her and to convince her to be with him," he said.

In discouraging anyone who might blame Elizabeth for her plight, Tennessee Bureau of Investigation Director Mark Gwyn, too, discounted the notion that there was a mutual romance.

"She is 15, a child. He is 50, a grown man. This is and was not a romance. This was manipulation solely to the benefit of Tad Cummins," Gwyn said.

Attorney Jason Whatley, who is representing Elizabeth's father, told CNN the kidnapping statute might not matter in Cummins' case, especially if he crossed state lines with Elizabeth, triggering federal kidnapping laws. He predicted the ex-teacher would face "scores of charges once we find him."

"I think Tad Cummins will have violated so many laws, I think he's finished," Whatley said.

The Tennessee Legislature is already in session, and the deadline for introducing legislation has passed, Cooper said. Before lawmakers convene again in January, the prosecutor intends to meet individually with legislators to convince them the law needs changing, he said.

An ideal law, he said, would presume that if a victim were younger than 18, he or she could not leave on his or her own accord. It would be similar to statutory rape laws that place the onus on adults not to break the law, he said.

Whatley said he concurs the law needs to be changed, but as a lawyer who also does defense work, he has reservations about the age limit. He'd hate seeing an 18-year-old accused of kidnapping for taking a 17-year-old on a date after the 17-year-old's parents forbade it, he said.

Perhaps the correct age is 16 and above, he said, suggesting that the amendment be called "Elizabeth's Law."

Amending the law makes sense, Cooper said, when you consider that, in Tennessee, children younger than 18 can't consent to sex, rent cars or enter into legal contracts.

"This is a much bigger life choice than trying to buy a car," he said of Elizabeth's case. "I think it would be a simple fix."