From Bearing Arms:

Idaho Sen. James Risch and California Rep. Darrel Issa are the primary sponsors of the “Freedom from Unfair Gun Taxes Act”, which Risch says would block states from imposing new excise taxes on the sale of firearms and ammunition that channels the revenue to gun control efforts. 

In a press release, Issa stated, “For years, extreme state policies and governors, including from my home state, have targeted the fundamental Second Amendment rights of our fellow Americans. California’s new imposition of a ‘sin tax’ on firearms and ammunition equates a core constitutional freedom with gambling or drug use. Enough is enough. That’s why Sen. Risch and I are joining forces to introduce this key legislation and stop any state tax that seeks to raise the price of self-defense out of reach for any American.”