Sgt. Thomas James Brennan after sustaining a concussion from a rocket-propelled grenade explosion during a battle against Taliban insurgents in southern Afghanistan in 2010. To the Editor: Thomas James Brennan makes a powerful case that military veterans deserve access to medical marijuana, which can help alleviate physical and mental war wounds (“ Why Pot, Not Pills, Works for My T.B.I., ” Op-Ed, Sept. 1). Mr. Brennan is correct that federal law prevents doctors in the Department of Veterans Affairs from prescribing medical cannabis. That’s the case for private doctors as well, since prescription is a federally regulated process and marijuana is a restricted Schedule I drug. But the only thing preventing V.A. doctors from recommending medical cannabis — the process that private providers in 29 states use to facilitate patient access — is the department’s own internal policy. Secretary David Shulkin recently said about marijuana that there is “some evidence that this is beginning to be helpful,” and President Trump said on the campaign trail that he personally knows “people that are very, very sick and for whatever reason, the marijuana really helps them.” If they really believe that, they should allow V.A. doctors to recommend cannabis to veterans who need it. All that is needed is a simple administrative fix that doesn’t require congressional action. TOM ANGELL, BROOKLYN The writer is chairman of Marijuana Majority, a nonprofit that works to reform the marijuana laws.