Hi, I am working in the US under a H1B visa. I am planning to get married married. My future husband would be visiting me but NOT WORKING in the US, probably under a H4 visa. He has his income in Switzerland. Would he become taxable under US law once we get married? Would he have to file a tax declaration? Would I have to include him in mine? Thanks

If you file joint return as residents, both of you must report worldwide income.
Or if your future husband completes SPT, for the resident period he must report worldwide income. Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income