A disabled veteran has told an appeals court that the department of veteran affairs policy on medical marijuana has caused him pain and significant economic harm, in a development campaigners say is a positive step in the battle to push for the drug's reclassification.

Michael Krawitz, one of five plaintiffs involved in a legal case before the court of appeal for the District of Columbia Circuit, told the Guardian that the VA denied him pain treatment after they discovered he had been prescribed medical marijuana while abroad.

He told the court in an affidavit that the withdrawal of care by the department, which has rated him 100% permanently disabled and thus eligible for all medical treatment under its auspices, has meant he now has to travel 130 miles from his home to see a doctor for pain relief.

Krawitz, 49, who is the executive director of Veterans for Medical Marijuana Access, said: "The bottom line is its unethical to take away someone's pain treatment. This conflicts with standards of medical care."

Krawitz sustained his injuries in a car accident while serving in the US air force, which has left him suffering debilitating pain.

The case, the result of a long-standing battle by medical marijuana advocates to reclassify the drug, is the first time in 20 years that scientific evidence regarding the therapeutic benefits of cannabis will be heard by a federal court.

This current case "looks more promising" than previous efforts, because of the court's focus on Krawitz and the request for more details, according to the ASA.

Joe Elford, the chief counsel with ASA, said: "It clearly demonstrated that the court is taking this case very seriously."

"This is something that demonstrates real harm to a real individual and that individual is Michael Krawitz.

"He is 100% disabled and supposed to get all his medical treatment from the VA. But because of the VA's policy on medical marijuana, which is clearly motivated by the schedule 1 status, that cannot happen."

After an initial oral hearing last week, the court ordered Americans for Safe Access, a advocacy group for medical marijuana use and research to file a brief in order to "clarify and amplify the assertions made [by] Michael Krawitz regarding his individual standing", and to "more fully explain precisely the nature of the injury that gives him standing".

ASA said they hope that if they can demonstrate that Krawitz was harmed by a federal policy that says medical marijuana has no medical value, they may also get the court to rule on the merit of the case. In that case, it would decide whether the scientific evidence is enough to reclassify the drug from its current status as a schedule 1 substance – as a dangerous drug on a par with heroin – to that of a safe drug that can be used in medicine.

The issue of "standing", of which the court sought more details, is a legal concept that restricts the right to sue to those who are directly harmed by what they are fighting and can get relief from a legal ruling. No plaintiffs were involved in the last appeal of the Drug Enforcement Agency's classification of the drug, and it was thrown out of court over the issue of standing.

There are veterans out there who are suffering

Krawitz had been receiving opiate-based pain relief from the VA until they discovered a prescription for medical marijuana he had received while abroad. They asked him to take a drug test and when he refused, they stopped his treatment.

"It said right there in the contract that if they find illegal drugs in your system they they will not give you any pain treatment," he said. "I found that offensive. I've been getting this pain treatment for years."

In an affidavit to the court, filed on Monday night which the Guardian has seen in draft form, Krawitz said he now has to travel to see a doctor 130 miles from his home in order to get pain treatment. The VA will not pay for this treatment, he said.

The affidavit details how his use of cannabis has allowed him to reduce his use of opiate-based drug oxycodone and has lessened the "deleterious side-effects" he had experienced.

He now divides his time between Oregon, the only state that allows non-residents to use medical marijuana, and his family's home state Virginia, where medical marijuana is illegal. His needs are now met by three different physicians, with his medical records split accordingly, he said.

Under the department's rules, veterans can be denied pain medication if they are found to be using illegal drugs. In 2010, the policy changed, to formally allow patients living in states where medical marijuana is legal to use it. VA doctors, however, are not allowed to prescribe it or recommend its use.

Krawitz said he has come across other veterans who, as a result of the VA's policy, or confusion over it, have been denied pain treatment.

"In the VA, it's really a big problem. There are veterans out there who are suffering."