A National Rifle Association lecture informed hundreds of people at the group’s annual meeting in Indianapolis on Friday how they could try to stop felony convictions and mental health problems preventing people from legally buying guns.

Attorneys, firearms retailers and rank-and-file members paid the lobby group up to $295 each for a day-long seminar which included a lengthy session on “mainstream and novel” techniques for restoring gun-ownership rights, such as scrubbing criminal records or challenging them in court.

Bryan Ciyou, an attorney and the author of several books on firearms law, told the closed event hosted by the NRA Foundation, the organisation's educational arm, that the number of people being ruled out of gun ownership in America represented “a frightening position for freedom”.

Arguing that historically only those guilty of “horrific crimes” had been excluded, he said President Barack Obama's administration had been determined to ban millions of Americans from owning guns since the shooting deaths of 20 young children and six staff at a Connecticut elementary school in December 2012. He warned attendees that the president’s gun-control efforts “pose the greatest risk to the Second Amendment of all time”.

“I believe that with the Sandy Hook shooting and the presidential directives that came down on 16 January 2013, that is a linchpin, a turning point moment in American law, that's going to have an impact, and which we are going to be talking about it in NRA seminars for now and for years in the future,” Ciyou said, addressing a packed hall in a downtown Indianapolis hotel.

Federal law has long barred Americans convicted of almost all felonies from possessing firearms or ammunition. Other groups are also restricted, such as those dishonourably discharged from the military, subject to domestic restraining orders, or judged to have serious mental health problems.

Earlier this year, the Obama administration proposed an executive action that would allow more health professionals to share the identities of people with a greater number of mental health problems with NICS, an FBI-run national criminal records database that is checked during most legal gun purchases.

Ciyou took care to stress that those convicted of the most serious felonies and those with the most dangerous mental health problems should not be allowed to access firearms. However, he dismissed Obama's proposals as “emotionally-driven”, and called the president's focus since Sandy Hook on the threat posed to children by guns a “red herring”.

He said the action risked disqualifying safe gun users who had seen a medic over minor depression. In his seminar literature, he pointed approvingly to state-based efforts that he said were “gaining momentum” as “a way to push back from the federal government”, such as “making it a crime for doctors and employers to ask about firearms possession”.

Several states have already passed laws that restore the right to bear arms to non-violent state felons who have served their punishments, and many others allow felons to petition for the restoration of their gun rights through the courts.

“The states are the ones you have to look to,” said Ciyou on Friday.

The NRA has in recent years played an influential role in lobbying for such state laws that loosen the restrictions on what weapons convicted felons may possess. An investigation by the New York Times in November 2011 found examples of felons who had committed violent crimes after having their gun rights restored.

On Friday, Ciyou directed his audience to a series of state-level techniques for restoring felons' right to own guns.

“Some state provisions include alternative misdemeanour sentencing statutes for felonies, expungement of old disqualifying crimes, and even to the more radical, such as nullification” of convictions, he pointed out in his literature.

Taking Indiana as his example, Ciyou explained that a convict with a three-year-old class D felony could petition the courts to have the offence reclassified as a class A misdemeanour. This “creates the situation that the felony never existed as a judgment of conviction” and “generally restores an individual's right to purchase firearms and pass a NICS background check”, he wrote.

Furthermore, given that the government’s list of factors disqualifying people from owning guns “continues to expand”, Ciyou wrote, “it may be prudent to consider sealing arrest records” that did not lead to a judgment or were reversed on appeal in a variety of other types of case.

Someone convicted of domestic violence, meanwhile, is entitled to petition an Indiana court to restore his or her right to possess a firearm five years later, Ciyou explained. Even if this is denied by the court, the convict can repeatedly re-apply every 12 months until it is granted.

The attorney also pointed to a growing number of “expungement statutes” in Indiana and other states, typically intended to help people with convictions secure jobs by hiding their criminal past from prospective employers, as potential avenues for attempts to restore gun rights.

“In theory, a person has not been convicted of a crime of domestic violence if the conviction has been expunged or if the person has been pardoned,” wrote Ciyou.

“We are doing something here today that really affects freedom in this country,” the attorney told his audience.

Facebook Twitter Pinterest Senator Marco Rubio speaks during the leadership forum at the NRA's annual meetings. Photograph: AJ Mast/AP

The gun lobby organisation’s annual meeting, which is expected to attract about 70,000 people, began on Friday. Senator Marco Rubio of Florida and former Senator Rick Santorum of Pennsylvania were among senior Republicans to address members at a leadership rally on Friday afternoon.

“Take comfort, because in just 32 months we will have a new president,” Rubio, who is expected to run for president in 2016, told the crowd.