Secretary of State John Kerry’s new interpretation of a law governing the production and exportation of military materiel will have a “crippling” effect on small-time gunsmiths, congressional Republicans warned.

The State Department’s Directorate of Defense Trade Controls issued “guidance” informing gunsmiths that they qualify as gun manufacturers under the International Traffic in Arms regulations, which require anyone “in the business of manufacturing or exporting or temporarily importing defense articles” to register with the State Department and pay a $2,250 fee. The mandate would have a “crippling fees and requirements” on gunsmiths, many of whom “make little to no income from their activities and often do it as a hobby or side business,” according to the lawmakers.